1 00:00:09,799 --> 00:00:14,850 start remember last time 2 00:00:14,850 --> 00:00:14,860 3 00:00:14,860 --> 00:00:18,420 we started Chapter twelve solids and 4 00:00:18,420 --> 00:00:18,430 we started Chapter twelve solids and 5 00:00:18,430 --> 00:00:21,689 we started Chapter twelve solids and modern materials let's look at what we 6 00:00:21,689 --> 00:00:21,699 modern materials let's look at what we 7 00:00:21,699 --> 00:00:24,830 modern materials let's look at what we have done in fact so far in this chapter 8 00:00:24,830 --> 00:00:24,840 have done in fact so far in this chapter 9 00:00:24,840 --> 00:00:28,769 have done in fact so far in this chapter we simply classify the solids according 10 00:00:28,769 --> 00:00:28,779 we simply classify the solids according 11 00:00:28,779 --> 00:00:32,400 we simply classify the solids according to the forces that holds the particle 12 00:00:32,400 --> 00:00:32,410 to the forces that holds the particle 13 00:00:32,410 --> 00:00:35,430 to the forces that holds the particle together in a solid and in this respect 14 00:00:35,430 --> 00:00:35,440 together in a solid and in this respect 15 00:00:35,440 --> 00:00:38,160 together in a solid and in this respect we classify them as metallic solids 16 00:00:38,160 --> 00:00:38,170 we classify them as metallic solids 17 00:00:38,170 --> 00:00:41,299 we classify them as metallic solids ionic solids covalent networks and 18 00:00:41,299 --> 00:00:41,309 ionic solids covalent networks and 19 00:00:41,309 --> 00:00:44,850 ionic solids covalent networks and molecular solids in addition to that we 20 00:00:44,850 --> 00:00:44,860 molecular solids in addition to that we 21 00:00:44,860 --> 00:00:51,020 molecular solids in addition to that we also have polymers and nano materials 22 00:00:51,020 --> 00:00:51,030 23 00:00:51,030 --> 00:00:54,690 now we also classified the solid into 24 00:00:54,690 --> 00:00:54,700 now we also classified the solid into 25 00:00:54,700 --> 00:00:57,569 now we also classified the solid into two as crystalline solids and amorphous 26 00:00:57,569 --> 00:00:57,579 two as crystalline solids and amorphous 27 00:00:57,579 --> 00:01:00,450 two as crystalline solids and amorphous solids crystalline solids are the solids 28 00:01:00,450 --> 00:01:00,460 solids crystalline solids are the solids 29 00:01:00,460 --> 00:01:03,560 solids crystalline solids are the solids which have a very regular pattern in 30 00:01:03,560 --> 00:01:03,570 which have a very regular pattern in 31 00:01:03,570 --> 00:01:06,810 which have a very regular pattern in 3-dimensional actually structure in 32 00:01:06,810 --> 00:01:06,820 3-dimensional actually structure in 33 00:01:06,820 --> 00:01:08,609 3-dimensional actually structure in their three-dimensional structure there 34 00:01:08,609 --> 00:01:08,619 their three-dimensional structure there 35 00:01:08,619 --> 00:01:11,490 their three-dimensional structure there is a repeating unit layer actually and 36 00:01:11,490 --> 00:01:11,500 is a repeating unit layer actually and 37 00:01:11,500 --> 00:01:14,340 is a repeating unit layer actually and that repeating unit we said is called 38 00:01:14,340 --> 00:01:14,350 that repeating unit we said is called 39 00:01:14,350 --> 00:01:19,200 that repeating unit we said is called the unit cell so the unit cell actually 40 00:01:19,200 --> 00:01:19,210 the unit cell so the unit cell actually 41 00:01:19,210 --> 00:01:22,350 the unit cell so the unit cell actually contains all the structural properties 42 00:01:22,350 --> 00:01:22,360 contains all the structural properties 43 00:01:22,360 --> 00:01:26,840 contains all the structural properties of the crystalline lattice and also 44 00:01:26,840 --> 00:01:26,850 of the crystalline lattice and also 45 00:01:26,850 --> 00:01:30,090 of the crystalline lattice and also tells you the atoms and the molecules 46 00:01:30,090 --> 00:01:30,100 tells you the atoms and the molecules 47 00:01:30,100 --> 00:01:33,570 tells you the atoms and the molecules whatever in the solid relative positions 48 00:01:33,570 --> 00:01:33,580 whatever in the solid relative positions 49 00:01:33,580 --> 00:01:36,719 whatever in the solid relative positions of those so the unit cell is very very 50 00:01:36,719 --> 00:01:36,729 of those so the unit cell is very very 51 00:01:36,729 --> 00:01:38,850 of those so the unit cell is very very important for crystalline solids now 52 00:01:38,850 --> 00:01:38,860 important for crystalline solids now 53 00:01:38,860 --> 00:01:40,920 important for crystalline solids now amorphous solids there is no regular 54 00:01:40,920 --> 00:01:40,930 amorphous solids there is no regular 55 00:01:40,930 --> 00:01:46,859 amorphous solids there is no regular pattern again no order of the atoms in 56 00:01:46,859 --> 00:01:46,869 pattern again no order of the atoms in 57 00:01:46,869 --> 00:01:50,160 pattern again no order of the atoms in the solid entry dimensions and they have 58 00:01:50,160 --> 00:01:50,170 the solid entry dimensions and they have 59 00:01:50,170 --> 00:01:51,660 the solid entry dimensions and they have different properties and it's very 60 00:01:51,660 --> 00:01:51,670 different properties and it's very 61 00:01:51,670 --> 00:01:55,170 different properties and it's very difficult to simply define more for 62 00:01:55,170 --> 00:01:55,180 difficult to simply define more for 63 00:01:55,180 --> 00:01:57,270 difficult to simply define more for solids because every time you have a 64 00:01:57,270 --> 00:01:57,280 solids because every time you have a 65 00:01:57,280 --> 00:01:59,490 solids because every time you have a different amorphous solids even though 66 00:01:59,490 --> 00:01:59,500 different amorphous solids even though 67 00:01:59,500 --> 00:02:03,780 different amorphous solids even though you have the same elements there and we 68 00:02:03,780 --> 00:02:03,790 you have the same elements there and we 69 00:02:03,790 --> 00:02:07,170 you have the same elements there and we also said that the crystalline solids 70 00:02:07,170 --> 00:02:07,180 also said that the crystalline solids 71 00:02:07,180 --> 00:02:10,410 also said that the crystalline solids have very sharp melting points but the 72 00:02:10,410 --> 00:02:10,420 have very sharp melting points but the 73 00:02:10,420 --> 00:02:12,240 have very sharp melting points but the amorphous solids do not have sharp 74 00:02:12,240 --> 00:02:12,250 amorphous solids do not have sharp 75 00:02:12,250 --> 00:02:14,429 amorphous solids do not have sharp melting points and we also said that we 76 00:02:14,429 --> 00:02:14,439 melting points and we also said that we 77 00:02:14,439 --> 00:02:18,059 melting points and we also said that we will simply study the crystalline solids 78 00:02:18,059 --> 00:02:18,069 will simply study the crystalline solids 79 00:02:18,069 --> 00:02:22,140 will simply study the crystalline solids here not the amorphous solids so we 80 00:02:22,140 --> 00:02:22,150 here not the amorphous solids so we 81 00:02:22,150 --> 00:02:24,780 here not the amorphous solids so we talked about the unit cells and ledges 82 00:02:24,780 --> 00:02:24,790 talked about the unit cells and ledges 83 00:02:24,790 --> 00:02:27,660 talked about the unit cells and ledges and lattice points actually lettuce is 84 00:02:27,660 --> 00:02:27,670 and lattice points actually lettuce is 85 00:02:27,670 --> 00:02:28,210 and lattice points actually lettuce is the 86 00:02:28,210 --> 00:02:28,220 the 87 00:02:28,220 --> 00:02:31,810 the three dimensional array of the 88 00:02:31,810 --> 00:02:31,820 three dimensional array of the 89 00:02:31,820 --> 00:02:35,350 three dimensional array of the crystalline structures and lattice 90 00:02:35,350 --> 00:02:35,360 crystalline structures and lattice 91 00:02:35,360 --> 00:02:38,230 crystalline structures and lattice points defines the lattice structure so 92 00:02:38,230 --> 00:02:38,240 points defines the lattice structure so 93 00:02:38,240 --> 00:02:41,110 points defines the lattice structure so we may have a atom or molecule at the 94 00:02:41,110 --> 00:02:41,120 we may have a atom or molecule at the 95 00:02:41,120 --> 00:02:43,240 we may have a atom or molecule at the lattice points or we may not but usually 96 00:02:43,240 --> 00:02:43,250 lattice points or we may not but usually 97 00:02:43,250 --> 00:02:46,330 lattice points or we may not but usually the lattice points are occupied by the 98 00:02:46,330 --> 00:02:46,340 the lattice points are occupied by the 99 00:02:46,340 --> 00:02:49,540 the lattice points are occupied by the atoms or the molecules of the solids 100 00:02:49,540 --> 00:02:49,550 atoms or the molecules of the solids 101 00:02:49,550 --> 00:02:53,110 atoms or the molecules of the solids again we talked about this how we define 102 00:02:53,110 --> 00:02:53,120 again we talked about this how we define 103 00:02:53,120 --> 00:02:55,000 again we talked about this how we define the lettuces and we said that there 104 00:02:55,000 --> 00:02:55,010 the lettuces and we said that there 105 00:02:55,010 --> 00:03:01,870 the lettuces and we said that there simply seven lettuces or I should 106 00:03:01,870 --> 00:03:01,880 simply seven lettuces or I should 107 00:03:01,880 --> 00:03:05,980 simply seven lettuces or I should probably call unit cell forms these are 108 00:03:05,980 --> 00:03:05,990 probably call unit cell forms these are 109 00:03:05,990 --> 00:03:09,870 probably call unit cell forms these are called the primitive unit cells and 110 00:03:09,870 --> 00:03:09,880 111 00:03:09,880 --> 00:03:12,790 cubic one is the most we will simply 112 00:03:12,790 --> 00:03:12,800 cubic one is the most we will simply 113 00:03:12,800 --> 00:03:15,790 cubic one is the most we will simply deal with in this chapter and maybe the 114 00:03:15,790 --> 00:03:15,800 deal with in this chapter and maybe the 115 00:03:15,800 --> 00:03:17,620 deal with in this chapter and maybe the others but the cubic is the most 116 00:03:17,620 --> 00:03:17,630 others but the cubic is the most 117 00:03:17,630 --> 00:03:21,850 others but the cubic is the most important then we can derive other unit 118 00:03:21,850 --> 00:03:21,860 important then we can derive other unit 119 00:03:21,860 --> 00:03:24,580 important then we can derive other unit cells or lattices in fact from those 120 00:03:24,580 --> 00:03:24,590 cells or lattices in fact from those 121 00:03:24,590 --> 00:03:31,030 cells or lattices in fact from those primitive lattices by simply placing an 122 00:03:31,030 --> 00:03:31,040 primitive lattices by simply placing an 123 00:03:31,040 --> 00:03:33,310 primitive lattices by simply placing an atom and the surface in the middle of 124 00:03:33,310 --> 00:03:33,320 atom and the surface in the middle of 125 00:03:33,320 --> 00:03:35,229 atom and the surface in the middle of the surface a surface of the unit cell 126 00:03:35,229 --> 00:03:35,239 the surface a surface of the unit cell 127 00:03:35,239 --> 00:03:38,020 the surface a surface of the unit cell or in the center of the unit cell or on 128 00:03:38,020 --> 00:03:38,030 or in the center of the unit cell or on 129 00:03:38,030 --> 00:03:41,290 or in the center of the unit cell or on middle of edges and so on and for 130 00:03:41,290 --> 00:03:41,300 middle of edges and so on and for 131 00:03:41,300 --> 00:03:43,510 middle of edges and so on and for example if we take the cubic unit cell 132 00:03:43,510 --> 00:03:43,520 example if we take the cubic unit cell 133 00:03:43,520 --> 00:03:46,090 example if we take the cubic unit cell there are three types of those one is 134 00:03:46,090 --> 00:03:46,100 there are three types of those one is 135 00:03:46,100 --> 00:03:49,420 there are three types of those one is that the primitive lattice primitive 136 00:03:49,420 --> 00:03:49,430 that the primitive lattice primitive 137 00:03:49,430 --> 00:03:52,660 that the primitive lattice primitive cubic actually and the other one is 138 00:03:52,660 --> 00:03:52,670 cubic actually and the other one is 139 00:03:52,670 --> 00:03:55,180 cubic actually and the other one is called body centered and the other one 140 00:03:55,180 --> 00:03:55,190 called body centered and the other one 141 00:03:55,190 --> 00:04:00,910 called body centered and the other one is called face centred body centered or 142 00:04:00,910 --> 00:04:00,920 is called face centred body centered or 143 00:04:00,920 --> 00:04:04,330 is called face centred body centered or face centered this is simply primitive 144 00:04:04,330 --> 00:04:04,340 face centered this is simply primitive 145 00:04:04,340 --> 00:04:06,759 face centered this is simply primitive cubic this is body centered cubic we 146 00:04:06,759 --> 00:04:06,769 cubic this is body centered cubic we 147 00:04:06,769 --> 00:04:09,040 cubic this is body centered cubic we have another atom right over here and 148 00:04:09,040 --> 00:04:09,050 have another atom right over here and 149 00:04:09,050 --> 00:04:12,610 have another atom right over here and face centered is we have a cube we have 150 00:04:12,610 --> 00:04:12,620 face centered is we have a cube we have 151 00:04:12,620 --> 00:04:16,420 face centered is we have a cube we have the atoms at the corner and also the 152 00:04:16,420 --> 00:04:16,430 the atoms at the corner and also the 153 00:04:16,430 --> 00:04:20,440 the atoms at the corner and also the atoms in the center of each faces so 154 00:04:20,440 --> 00:04:20,450 atoms in the center of each faces so 155 00:04:20,450 --> 00:04:23,110 atoms in the center of each faces so these that we should simply be familiar 156 00:04:23,110 --> 00:04:23,120 these that we should simply be familiar 157 00:04:23,120 --> 00:04:26,710 these that we should simply be familiar with because we will be using those in 158 00:04:26,710 --> 00:04:26,720 with because we will be using those in 159 00:04:26,720 --> 00:04:29,050 with because we will be using those in this chapter so what we said again this 160 00:04:29,050 --> 00:04:29,060 this chapter so what we said again this 161 00:04:29,060 --> 00:04:31,810 this chapter so what we said again this simply says that the lattice points may 162 00:04:31,810 --> 00:04:31,820 simply says that the lattice points may 163 00:04:31,820 --> 00:04:36,040 simply says that the lattice points may be occupied by atoms molecules or group 164 00:04:36,040 --> 00:04:36,050 be occupied by atoms molecules or group 165 00:04:36,050 --> 00:04:39,520 be occupied by atoms molecules or group of other atoms and those groups that 166 00:04:39,520 --> 00:04:39,530 of other atoms and those groups that 167 00:04:39,530 --> 00:04:41,800 of other atoms and those groups that occupies the lattice points 168 00:04:41,800 --> 00:04:41,810 occupies the lattice points 169 00:04:41,810 --> 00:04:45,760 occupies the lattice points are called motives we talk about that 170 00:04:45,760 --> 00:04:45,770 are called motives we talk about that 171 00:04:45,770 --> 00:04:48,790 are called motives we talk about that now when we consider the metallic 172 00:04:48,790 --> 00:04:48,800 now when we consider the metallic 173 00:04:48,800 --> 00:04:51,550 now when we consider the metallic structures it would be very easy 174 00:04:51,550 --> 00:04:51,560 structures it would be very easy 175 00:04:51,560 --> 00:04:57,810 structures it would be very easy actually to consider the solid metal 176 00:04:57,810 --> 00:04:57,820 actually to consider the solid metal 177 00:04:57,820 --> 00:05:01,150 actually to consider the solid metal structures because metallic solids 178 00:05:01,150 --> 00:05:01,160 structures because metallic solids 179 00:05:01,160 --> 00:05:03,970 structures because metallic solids metals in the solids are crystalline 180 00:05:03,970 --> 00:05:03,980 metals in the solids are crystalline 181 00:05:03,980 --> 00:05:07,180 metals in the solids are crystalline solids and the unit in that case our 182 00:05:07,180 --> 00:05:07,190 solids and the unit in that case our 183 00:05:07,190 --> 00:05:10,960 solids and the unit in that case our metal atoms right so metal atoms occupy 184 00:05:10,960 --> 00:05:10,970 metal atoms right so metal atoms occupy 185 00:05:10,970 --> 00:05:15,670 metal atoms right so metal atoms occupy the lattice points and I mean you may 186 00:05:15,670 --> 00:05:15,680 the lattice points and I mean you may 187 00:05:15,680 --> 00:05:20,050 the lattice points and I mean you may have simply primitive lattice or you may 188 00:05:20,050 --> 00:05:20,060 have simply primitive lattice or you may 189 00:05:20,060 --> 00:05:21,850 have simply primitive lattice or you may have body centered or you may have face 190 00:05:21,850 --> 00:05:21,860 have body centered or you may have face 191 00:05:21,860 --> 00:05:26,350 have body centered or you may have face centered type lattices now the metals 192 00:05:26,350 --> 00:05:26,360 centered type lattices now the metals 193 00:05:26,360 --> 00:05:30,580 centered type lattices now the metals are all same sized atoms so you can 194 00:05:30,580 --> 00:05:30,590 are all same sized atoms so you can 195 00:05:30,590 --> 00:05:35,560 are all same sized atoms so you can simply consider metal as if collections 196 00:05:35,560 --> 00:05:35,570 simply consider metal as if collections 197 00:05:35,570 --> 00:05:40,420 simply consider metal as if collections of the same sized sized spheres right so 198 00:05:40,420 --> 00:05:40,430 of the same sized sized spheres right so 199 00:05:40,430 --> 00:05:42,970 of the same sized sized spheres right so when you simply consider as metal atoms 200 00:05:42,970 --> 00:05:42,980 when you simply consider as metal atoms 201 00:05:42,980 --> 00:05:46,630 when you simply consider as metal atoms that's fair here the lattice structures 202 00:05:46,630 --> 00:05:46,640 that's fair here the lattice structures 203 00:05:46,640 --> 00:05:49,090 that's fair here the lattice structures or the unit cell would look like this 204 00:05:49,090 --> 00:05:49,100 or the unit cell would look like this 205 00:05:49,100 --> 00:05:52,390 or the unit cell would look like this again the primitive unit cells and body 206 00:05:52,390 --> 00:05:52,400 again the primitive unit cells and body 207 00:05:52,400 --> 00:05:56,190 again the primitive unit cells and body centered and face centered and so on now 208 00:05:56,190 --> 00:05:56,200 centered and face centered and so on now 209 00:05:56,200 --> 00:06:00,610 centered and face centered and so on now actually the unit cell is the part that 210 00:06:00,610 --> 00:06:00,620 actually the unit cell is the part that 211 00:06:00,620 --> 00:06:05,590 actually the unit cell is the part that is inside of the cube drawn here as a 212 00:06:05,590 --> 00:06:05,600 is inside of the cube drawn here as a 213 00:06:05,600 --> 00:06:09,040 is inside of the cube drawn here as a matter of fact so when you have a metal 214 00:06:09,040 --> 00:06:09,050 matter of fact so when you have a metal 215 00:06:09,050 --> 00:06:12,159 matter of fact so when you have a metal atom or a sphere at the corner of the 216 00:06:12,159 --> 00:06:12,169 atom or a sphere at the corner of the 217 00:06:12,169 --> 00:06:16,240 atom or a sphere at the corner of the cube that is shared by eight cubes or 218 00:06:16,240 --> 00:06:16,250 cube that is shared by eight cubes or 219 00:06:16,250 --> 00:06:18,940 cube that is shared by eight cubes or eight unit cells only one-eighth of 220 00:06:18,940 --> 00:06:18,950 eight unit cells only one-eighth of 221 00:06:18,950 --> 00:06:22,180 eight unit cells only one-eighth of those is in this and if the in the body 222 00:06:22,180 --> 00:06:22,190 those is in this and if the in the body 223 00:06:22,190 --> 00:06:23,710 those is in this and if the in the body centered actually the one in the middle 224 00:06:23,710 --> 00:06:23,720 centered actually the one in the middle 225 00:06:23,720 --> 00:06:26,740 centered actually the one in the middle is not shared by any others and face 226 00:06:26,740 --> 00:06:26,750 is not shared by any others and face 227 00:06:26,750 --> 00:06:29,200 is not shared by any others and face centered ones the ones which in the 228 00:06:29,200 --> 00:06:29,210 centered ones the ones which in the 229 00:06:29,210 --> 00:06:31,540 centered ones the ones which in the middle of the face are shared by two 230 00:06:31,540 --> 00:06:31,550 middle of the face are shared by two 231 00:06:31,550 --> 00:06:35,350 middle of the face are shared by two unit cells so considering that we simply 232 00:06:35,350 --> 00:06:35,360 unit cells so considering that we simply 233 00:06:35,360 --> 00:06:37,990 unit cells so considering that we simply said that if we try to find out how many 234 00:06:37,990 --> 00:06:38,000 said that if we try to find out how many 235 00:06:38,000 --> 00:06:42,130 said that if we try to find out how many metal atoms belongs to one unit cell or 236 00:06:42,130 --> 00:06:42,140 metal atoms belongs to one unit cell or 237 00:06:42,140 --> 00:06:47,620 metal atoms belongs to one unit cell or how many or let's say let's say this way 238 00:06:47,620 --> 00:06:47,630 how many or let's say let's say this way 239 00:06:47,630 --> 00:06:50,440 how many or let's say let's say this way how many metal atoms corresponds to one 240 00:06:50,440 --> 00:06:50,450 how many metal atoms corresponds to one 241 00:06:50,450 --> 00:06:53,590 how many metal atoms corresponds to one unit cell for the simple cubic unit cell 242 00:06:53,590 --> 00:06:53,600 unit cell for the simple cubic unit cell 243 00:06:53,600 --> 00:06:55,000 unit cell for the simple cubic unit cell cases 244 00:06:55,000 --> 00:06:55,010 cases 245 00:06:55,010 --> 00:06:57,760 cases eight corners we have eight metal atoms 246 00:06:57,760 --> 00:06:57,770 eight corners we have eight metal atoms 247 00:06:57,770 --> 00:07:01,780 eight corners we have eight metal atoms and one over eight of those only in the 248 00:07:01,780 --> 00:07:01,790 and one over eight of those only in the 249 00:07:01,790 --> 00:07:04,180 and one over eight of those only in the unit cell here cubic unit cell so that 250 00:07:04,180 --> 00:07:04,190 unit cell here cubic unit cell so that 251 00:07:04,190 --> 00:07:07,780 unit cell here cubic unit cell so that simply makes one atom per unit cell now 252 00:07:07,780 --> 00:07:07,790 simply makes one atom per unit cell now 253 00:07:07,790 --> 00:07:12,700 simply makes one atom per unit cell now here in the body centered two atoms per 254 00:07:12,700 --> 00:07:12,710 here in the body centered two atoms per 255 00:07:12,710 --> 00:07:15,340 here in the body centered two atoms per unit cell one comes from the corner 256 00:07:15,340 --> 00:07:15,350 unit cell one comes from the corner 257 00:07:15,350 --> 00:07:17,800 unit cell one comes from the corner eight corners and one in the middle and 258 00:07:17,800 --> 00:07:17,810 eight corners and one in the middle and 259 00:07:17,810 --> 00:07:20,680 eight corners and one in the middle and in the face center case we have simply 260 00:07:20,680 --> 00:07:20,690 in the face center case we have simply 261 00:07:20,690 --> 00:07:22,540 in the face center case we have simply one coming from the corners and three 262 00:07:22,540 --> 00:07:22,550 one coming from the corners and three 263 00:07:22,550 --> 00:07:25,690 one coming from the corners and three from the faces six faces and that makes 264 00:07:25,690 --> 00:07:25,700 from the faces six faces and that makes 265 00:07:25,700 --> 00:07:30,370 from the faces six faces and that makes that two actually three four metal atoms 266 00:07:30,370 --> 00:07:30,380 that two actually three four metal atoms 267 00:07:30,380 --> 00:07:34,900 that two actually three four metal atoms makes a face centred unit cell or face 268 00:07:34,900 --> 00:07:34,910 makes a face centred unit cell or face 269 00:07:34,910 --> 00:07:37,750 makes a face centred unit cell or face centered unit cell is made of four atoms 270 00:07:37,750 --> 00:07:37,760 centered unit cell is made of four atoms 271 00:07:37,760 --> 00:07:40,510 centered unit cell is made of four atoms metal atoms now again they are all same 272 00:07:40,510 --> 00:07:40,520 metal atoms now again they are all same 273 00:07:40,520 --> 00:07:48,730 metal atoms now again they are all same size same diameters now then we simply 274 00:07:48,730 --> 00:07:48,740 size same diameters now then we simply 275 00:07:48,740 --> 00:07:51,730 size same diameters now then we simply talk about close packed structures what 276 00:07:51,730 --> 00:07:51,740 talk about close packed structures what 277 00:07:51,740 --> 00:07:53,560 talk about close packed structures what is the close packed structures that 278 00:07:53,560 --> 00:07:53,570 is the close packed structures that 279 00:07:53,570 --> 00:08:00,280 is the close packed structures that simply says how can we pack same size of 280 00:08:00,280 --> 00:08:00,290 simply says how can we pack same size of 281 00:08:00,290 --> 00:08:05,440 simply says how can we pack same size of spheres in a given volume such that we 282 00:08:05,440 --> 00:08:05,450 spheres in a given volume such that we 283 00:08:05,450 --> 00:08:08,080 spheres in a given volume such that we will put maximum number of spheres in 284 00:08:08,080 --> 00:08:08,090 will put maximum number of spheres in 285 00:08:08,090 --> 00:08:11,830 will put maximum number of spheres in that volume so there are two ways of 286 00:08:11,830 --> 00:08:11,840 that volume so there are two ways of 287 00:08:11,840 --> 00:08:15,100 that volume so there are two ways of stacking those same size fares or you 288 00:08:15,100 --> 00:08:15,110 stacking those same size fares or you 289 00:08:15,110 --> 00:08:18,940 stacking those same size fares or you can call it metal atoms actually which 290 00:08:18,940 --> 00:08:18,950 can call it metal atoms actually which 291 00:08:18,950 --> 00:08:22,330 can call it metal atoms actually which belongs to the close packing lattice or 292 00:08:22,330 --> 00:08:22,340 belongs to the close packing lattice or 293 00:08:22,340 --> 00:08:27,510 belongs to the close packing lattice or post packing arrays in fact and one is 294 00:08:27,510 --> 00:08:27,520 post packing arrays in fact and one is 295 00:08:27,520 --> 00:08:31,060 post packing arrays in fact and one is you have one layer of spheres put 296 00:08:31,060 --> 00:08:31,070 you have one layer of spheres put 297 00:08:31,070 --> 00:08:33,940 you have one layer of spheres put together as close as possible and then 298 00:08:33,940 --> 00:08:33,950 together as close as possible and then 299 00:08:33,950 --> 00:08:35,770 together as close as possible and then you have the second layer of spheres 300 00:08:35,770 --> 00:08:35,780 you have the second layer of spheres 301 00:08:35,780 --> 00:08:38,560 you have the second layer of spheres again put close as close as possible in 302 00:08:38,560 --> 00:08:38,570 again put close as close as possible in 303 00:08:38,570 --> 00:08:41,230 again put close as close as possible in that layer but they put on that sort of 304 00:08:41,230 --> 00:08:41,240 that layer but they put on that sort of 305 00:08:41,240 --> 00:08:43,540 that layer but they put on that sort of little bit displaced not on the top of 306 00:08:43,540 --> 00:08:43,550 little bit displaced not on the top of 307 00:08:43,550 --> 00:08:46,000 little bit displaced not on the top of the first then you may have the third 308 00:08:46,000 --> 00:08:46,010 the first then you may have the third 309 00:08:46,010 --> 00:08:48,910 the first then you may have the third layer as we said right on the top of the 310 00:08:48,910 --> 00:08:48,920 layer as we said right on the top of the 311 00:08:48,920 --> 00:08:52,140 layer as we said right on the top of the first or you can put it in a different 312 00:08:52,140 --> 00:08:52,150 first or you can put it in a different 313 00:08:52,150 --> 00:08:56,320 first or you can put it in a different place actually then the first layer so 314 00:08:56,320 --> 00:08:56,330 place actually then the first layer so 315 00:08:56,330 --> 00:08:59,290 place actually then the first layer so if I have this type of stacking I will 316 00:08:59,290 --> 00:08:59,300 if I have this type of stacking I will 317 00:08:59,300 --> 00:09:03,520 if I have this type of stacking I will have a Bab type close packing structure 318 00:09:03,520 --> 00:09:03,530 have a Bab type close packing structure 319 00:09:03,530 --> 00:09:05,140 have a Bab type close packing structure and the unit cell in this case is 320 00:09:05,140 --> 00:09:05,150 and the unit cell in this case is 321 00:09:05,150 --> 00:09:07,900 and the unit cell in this case is hexagonal and that is called hexagonal 322 00:09:07,900 --> 00:09:07,910 hexagonal and that is called hexagonal 323 00:09:07,910 --> 00:09:08,380 hexagonal and that is called hexagonal close 324 00:09:08,380 --> 00:09:08,390 close 325 00:09:08,390 --> 00:09:11,940 close pack an HCP and if I have this type of 326 00:09:11,940 --> 00:09:11,950 pack an HCP and if I have this type of 327 00:09:11,950 --> 00:09:17,800 pack an HCP and if I have this type of packing again ABC ABC ABC that and the 328 00:09:17,800 --> 00:09:17,810 packing again ABC ABC ABC that and the 329 00:09:17,810 --> 00:09:19,750 packing again ABC ABC ABC that and the unit cell in this case is face centered 330 00:09:19,750 --> 00:09:19,760 unit cell in this case is face centered 331 00:09:19,760 --> 00:09:22,600 unit cell in this case is face centered cubic and it's called cubic close 332 00:09:22,600 --> 00:09:22,610 cubic and it's called cubic close 333 00:09:22,610 --> 00:09:25,150 cubic and it's called cubic close packing type structures this simply 334 00:09:25,150 --> 00:09:25,160 packing type structures this simply 335 00:09:25,160 --> 00:09:29,170 packing type structures this simply shows the unit cell of this packing and 336 00:09:29,170 --> 00:09:29,180 shows the unit cell of this packing and 337 00:09:29,180 --> 00:09:31,840 shows the unit cell of this packing and the this one also now what we said again 338 00:09:31,840 --> 00:09:31,850 the this one also now what we said again 339 00:09:31,850 --> 00:09:35,470 the this one also now what we said again in these two cases both are close back 340 00:09:35,470 --> 00:09:35,480 in these two cases both are close back 341 00:09:35,480 --> 00:09:38,590 in these two cases both are close back and even though the unit cells are 342 00:09:38,590 --> 00:09:38,600 and even though the unit cells are 343 00:09:38,600 --> 00:09:40,150 and even though the unit cells are different the only things is the unit 344 00:09:40,150 --> 00:09:40,160 different the only things is the unit 345 00:09:40,160 --> 00:09:41,890 different the only things is the unit cells are different I should probably 346 00:09:41,890 --> 00:09:41,900 cells are different I should probably 347 00:09:41,900 --> 00:09:45,010 cells are different I should probably put it back again they have exactly the 348 00:09:45,010 --> 00:09:45,020 put it back again they have exactly the 349 00:09:45,020 --> 00:09:48,720 put it back again they have exactly the same problem een in terms of packing 350 00:09:48,720 --> 00:09:48,730 same problem een in terms of packing 351 00:09:48,730 --> 00:09:51,670 same problem een in terms of packing maximum number of spheres in a given 352 00:09:51,670 --> 00:09:51,680 maximum number of spheres in a given 353 00:09:51,680 --> 00:09:53,230 maximum number of spheres in a given volume they are the same exactly the 354 00:09:53,230 --> 00:09:53,240 volume they are the same exactly the 355 00:09:53,240 --> 00:09:58,800 volume they are the same exactly the same now in both cases actually we have 356 00:09:58,800 --> 00:09:58,810 same now in both cases actually we have 357 00:09:58,810 --> 00:10:03,010 same now in both cases actually we have holes between the spheres 358 00:10:03,010 --> 00:10:03,020 holes between the spheres 359 00:10:03,020 --> 00:10:05,830 holes between the spheres holes between the spheres and those are 360 00:10:05,830 --> 00:10:05,840 holes between the spheres and those are 361 00:10:05,840 --> 00:10:11,220 holes between the spheres and those are simply called tetrahedral holes and 362 00:10:11,220 --> 00:10:11,230 simply called tetrahedral holes and 363 00:10:11,230 --> 00:10:16,600 simply called tetrahedral holes and octahedral holes let's say holes let me 364 00:10:16,600 --> 00:10:16,610 octahedral holes let's say holes let me 365 00:10:16,610 --> 00:10:17,470 octahedral holes let's say holes let me write it down 366 00:10:17,470 --> 00:10:17,480 write it down 367 00:10:17,480 --> 00:10:26,460 write it down pause in closed bag closed packed 368 00:10:26,460 --> 00:10:26,470 pause in closed bag closed packed 369 00:10:26,470 --> 00:10:35,170 pause in closed bag closed packed letters now one type of hole is formed 370 00:10:35,170 --> 00:10:35,180 letters now one type of hole is formed 371 00:10:35,180 --> 00:10:41,200 letters now one type of hole is formed by four spheres and it would be like 372 00:10:41,200 --> 00:10:41,210 by four spheres and it would be like 373 00:10:41,210 --> 00:10:44,110 by four spheres and it would be like this this is the second sphere and the 374 00:10:44,110 --> 00:10:44,120 this this is the second sphere and the 375 00:10:44,120 --> 00:10:46,780 this this is the second sphere and the third one here like this and then we 376 00:10:46,780 --> 00:10:46,790 third one here like this and then we 377 00:10:46,790 --> 00:10:50,020 third one here like this and then we have the fourth one is right on the top 378 00:10:50,020 --> 00:10:50,030 have the fourth one is right on the top 379 00:10:50,030 --> 00:10:55,930 have the fourth one is right on the top of this just fill in that now there is a 380 00:10:55,930 --> 00:10:55,940 of this just fill in that now there is a 381 00:10:55,940 --> 00:11:00,070 of this just fill in that now there is a hole between these four spheres in a 382 00:11:00,070 --> 00:11:00,080 hole between these four spheres in a 383 00:11:00,080 --> 00:11:01,810 hole between these four spheres in a closed pack structure in both cases 384 00:11:01,810 --> 00:11:01,820 closed pack structure in both cases 385 00:11:01,820 --> 00:11:06,580 closed pack structure in both cases actually and if you consider the center 386 00:11:06,580 --> 00:11:06,590 actually and if you consider the center 387 00:11:06,590 --> 00:11:09,970 actually and if you consider the center of these four spheres they are right on 388 00:11:09,970 --> 00:11:09,980 of these four spheres they are right on 389 00:11:09,980 --> 00:11:14,980 of these four spheres they are right on the corner of a tetrahedron right on the 390 00:11:14,980 --> 00:11:14,990 the corner of a tetrahedron right on the 391 00:11:14,990 --> 00:11:17,350 the corner of a tetrahedron right on the corner of a tetrahedron therefore this 392 00:11:17,350 --> 00:11:17,360 corner of a tetrahedron therefore this 393 00:11:17,360 --> 00:11:21,870 corner of a tetrahedron therefore this type of holes is called tetrahedral 394 00:11:21,870 --> 00:11:21,880 type of holes is called tetrahedral 395 00:11:21,880 --> 00:11:25,820 type of holes is called tetrahedral tetrahedral holes let's say here 396 00:11:25,820 --> 00:11:25,830 tetrahedral holes let's say here 397 00:11:25,830 --> 00:11:33,960 tetrahedral holes let's say here tetrahedral holes or these are simply 398 00:11:33,960 --> 00:11:33,970 tetrahedral holes or these are simply 399 00:11:33,970 --> 00:11:36,690 tetrahedral holes or these are simply sites there sometime called site 400 00:11:36,690 --> 00:11:36,700 sites there sometime called site 401 00:11:36,700 --> 00:11:39,390 sites there sometime called site tetrahedral site so there is a space 402 00:11:39,390 --> 00:11:39,400 tetrahedral site so there is a space 403 00:11:39,400 --> 00:11:41,190 tetrahedral site so there is a space between them that's a tetrahedral holes 404 00:11:41,190 --> 00:11:41,200 between them that's a tetrahedral holes 405 00:11:41,200 --> 00:11:44,060 between them that's a tetrahedral holes now the question here is how many 406 00:11:44,060 --> 00:11:44,070 now the question here is how many 407 00:11:44,070 --> 00:11:47,490 now the question here is how many tetrahedral holes can we obtain if I 408 00:11:47,490 --> 00:11:47,500 tetrahedral holes can we obtain if I 409 00:11:47,500 --> 00:11:53,190 tetrahedral holes can we obtain if I packed n spheres and spheres and the 410 00:11:53,190 --> 00:11:53,200 packed n spheres and spheres and the 411 00:11:53,200 --> 00:11:55,260 packed n spheres and spheres and the answer again that can be fine 412 00:11:55,260 --> 00:11:55,270 answer again that can be fine 413 00:11:55,270 --> 00:11:59,300 answer again that can be fine we will have two and tetrahedral holes 414 00:11:59,300 --> 00:11:59,310 we will have two and tetrahedral holes 415 00:11:59,310 --> 00:12:07,160 we will have two and tetrahedral holes so n n closed let's say close packed 416 00:12:07,160 --> 00:12:07,170 417 00:12:07,170 --> 00:12:15,950 structure structure will have two and 418 00:12:15,950 --> 00:12:15,960 structure structure will have two and 419 00:12:15,960 --> 00:12:23,540 structure structure will have two and tetrahedral holes tetrahedral holes 420 00:12:23,540 --> 00:12:23,550 tetrahedral holes tetrahedral holes 421 00:12:23,550 --> 00:12:28,680 tetrahedral holes tetrahedral holes tetrahedral holes now if you have also 422 00:12:28,680 --> 00:12:28,690 tetrahedral holes now if you have also 423 00:12:28,690 --> 00:12:31,230 tetrahedral holes now if you have also another type of holes here and that is 424 00:12:31,230 --> 00:12:31,240 another type of holes here and that is 425 00:12:31,240 --> 00:12:34,290 another type of holes here and that is called octahedral holes and that would 426 00:12:34,290 --> 00:12:34,300 called octahedral holes and that would 427 00:12:34,300 --> 00:12:40,260 called octahedral holes and that would be between the space of six equal sized 428 00:12:40,260 --> 00:12:40,270 be between the space of six equal sized 429 00:12:40,270 --> 00:12:43,920 be between the space of six equal sized fairs now how can we show that we can 430 00:12:43,920 --> 00:12:43,930 fairs now how can we show that we can 431 00:12:43,930 --> 00:12:46,320 fairs now how can we show that we can draw it again as follow this is one 432 00:12:46,320 --> 00:12:46,330 draw it again as follow this is one 433 00:12:46,330 --> 00:12:52,100 draw it again as follow this is one sphere and this is another same size 434 00:12:52,100 --> 00:12:52,110 435 00:12:52,110 --> 00:12:55,110 another one over here now again this is 436 00:12:55,110 --> 00:12:55,120 another one over here now again this is 437 00:12:55,120 --> 00:13:00,600 another one over here now again this is just a square like this now I put 438 00:13:00,600 --> 00:13:00,610 just a square like this now I put 439 00:13:00,610 --> 00:13:05,480 just a square like this now I put another sphere on the top of this and 440 00:13:05,480 --> 00:13:05,490 another sphere on the top of this and 441 00:13:05,490 --> 00:13:10,350 another sphere on the top of this and also below let's say if I put a sphere 442 00:13:10,350 --> 00:13:10,360 also below let's say if I put a sphere 443 00:13:10,360 --> 00:13:14,280 also below let's say if I put a sphere on the top here like this 444 00:13:14,280 --> 00:13:14,290 on the top here like this 445 00:13:14,290 --> 00:13:16,830 on the top here like this now another sphere in the bottom on the 446 00:13:16,830 --> 00:13:16,840 now another sphere in the bottom on the 447 00:13:16,840 --> 00:13:21,090 now another sphere in the bottom on the other side considering that these four 448 00:13:21,090 --> 00:13:21,100 other side considering that these four 449 00:13:21,100 --> 00:13:23,160 other side considering that these four all in the same layer let's say we have 450 00:13:23,160 --> 00:13:23,170 all in the same layer let's say we have 451 00:13:23,170 --> 00:13:26,370 all in the same layer let's say we have another one on the other side like this 452 00:13:26,370 --> 00:13:26,380 another one on the other side like this 453 00:13:26,380 --> 00:13:33,170 another one on the other side like this so now I have a whole space between six 454 00:13:33,170 --> 00:13:33,180 so now I have a whole space between six 455 00:13:33,180 --> 00:13:35,220 so now I have a whole space between six atoms or six 456 00:13:35,220 --> 00:13:35,230 atoms or six 457 00:13:35,230 --> 00:13:37,950 atoms or six Phares you can say same-size fares now 458 00:13:37,950 --> 00:13:37,960 Phares you can say same-size fares now 459 00:13:37,960 --> 00:13:41,490 Phares you can say same-size fares now if you consider the center of these six 460 00:13:41,490 --> 00:13:41,500 if you consider the center of these six 461 00:13:41,500 --> 00:13:44,400 if you consider the center of these six spheres one here one the other side one 462 00:13:44,400 --> 00:13:44,410 spheres one here one the other side one 463 00:13:44,410 --> 00:13:47,760 spheres one here one the other side one on their side it is they are all on the 464 00:13:47,760 --> 00:13:47,770 on their side it is they are all on the 465 00:13:47,770 --> 00:13:51,750 on their side it is they are all on the corner of an octahedron on the corner of 466 00:13:51,750 --> 00:13:51,760 corner of an octahedron on the corner of 467 00:13:51,760 --> 00:13:54,510 corner of an octahedron on the corner of an octahedron therefore this is simply 468 00:13:54,510 --> 00:13:54,520 an octahedron therefore this is simply 469 00:13:54,520 --> 00:14:03,800 an octahedron therefore this is simply called octahedral poles octahedral holes 470 00:14:03,800 --> 00:14:03,810 called octahedral poles octahedral holes 471 00:14:03,810 --> 00:14:08,520 called octahedral poles octahedral holes or sites you can see that in some book 472 00:14:08,520 --> 00:14:08,530 or sites you can see that in some book 473 00:14:08,530 --> 00:14:12,150 or sites you can see that in some book that's called its sides and now if I 474 00:14:12,150 --> 00:14:12,160 that's called its sides and now if I 475 00:14:12,160 --> 00:14:16,500 that's called its sides and now if I have impact closed structure and number 476 00:14:16,500 --> 00:14:16,510 have impact closed structure and number 477 00:14:16,510 --> 00:14:19,200 have impact closed structure and number of using M number of atoms if I get a 478 00:14:19,200 --> 00:14:19,210 of using M number of atoms if I get a 479 00:14:19,210 --> 00:14:21,510 of using M number of atoms if I get a close packed structure the number of 480 00:14:21,510 --> 00:14:21,520 close packed structure the number of 481 00:14:21,520 --> 00:14:24,480 close packed structure the number of octahedral holes is equal to the number 482 00:14:24,480 --> 00:14:24,490 octahedral holes is equal to the number 483 00:14:24,490 --> 00:14:27,180 octahedral holes is equal to the number of spheres I packed so I will simply 484 00:14:27,180 --> 00:14:27,190 of spheres I packed so I will simply 485 00:14:27,190 --> 00:14:35,520 of spheres I packed so I will simply have n both the he drill holes if I 486 00:14:35,520 --> 00:14:35,530 have n both the he drill holes if I 487 00:14:35,530 --> 00:14:39,750 have n both the he drill holes if I simply pack n number of spheres in a 488 00:14:39,750 --> 00:14:39,760 simply pack n number of spheres in a 489 00:14:39,760 --> 00:14:43,200 simply pack n number of spheres in a close-packed structure I will have n 490 00:14:43,200 --> 00:14:43,210 close-packed structure I will have n 491 00:14:43,210 --> 00:14:46,290 close-packed structure I will have n number of octahedral holes octahedral 492 00:14:46,290 --> 00:14:46,300 number of octahedral holes octahedral 493 00:14:46,300 --> 00:14:48,510 number of octahedral holes octahedral holes now these are important actually 494 00:14:48,510 --> 00:14:48,520 holes now these are important actually 495 00:14:48,520 --> 00:14:52,410 holes now these are important actually because when we talk about the ionic 496 00:14:52,410 --> 00:14:52,420 because when we talk about the ionic 497 00:14:52,420 --> 00:14:54,540 because when we talk about the ionic compounds ionic solids we will see that 498 00:14:54,540 --> 00:14:54,550 compounds ionic solids we will see that 499 00:14:54,550 --> 00:14:57,180 compounds ionic solids we will see that these holes tetrahedral or octahedral 500 00:14:57,180 --> 00:14:57,190 these holes tetrahedral or octahedral 501 00:14:57,190 --> 00:15:01,560 these holes tetrahedral or octahedral holes are filled with ions are filled 502 00:15:01,560 --> 00:15:01,570 holes are filled with ions are filled 503 00:15:01,570 --> 00:15:05,010 holes are filled with ions are filled with ions again you can simply see that 504 00:15:05,010 --> 00:15:05,020 with ions again you can simply see that 505 00:15:05,020 --> 00:15:08,010 with ions again you can simply see that the octahedral holes will be little 506 00:15:08,010 --> 00:15:08,020 the octahedral holes will be little 507 00:15:08,020 --> 00:15:10,770 the octahedral holes will be little larger than the tetrahedral holes right 508 00:15:10,770 --> 00:15:10,780 larger than the tetrahedral holes right 509 00:15:10,780 --> 00:15:13,440 larger than the tetrahedral holes right tetrahedron swaps so both of those close 510 00:15:13,440 --> 00:15:13,450 tetrahedron swaps so both of those close 511 00:15:13,450 --> 00:15:15,540 tetrahedron swaps so both of those close packed structures in fact have these 512 00:15:15,540 --> 00:15:15,550 packed structures in fact have these 513 00:15:15,550 --> 00:15:17,970 packed structures in fact have these holes and the number of holes with 514 00:15:17,970 --> 00:15:17,980 holes and the number of holes with 515 00:15:17,980 --> 00:15:21,030 holes and the number of holes with respect to the number of atoms that form 516 00:15:21,030 --> 00:15:21,040 respect to the number of atoms that form 517 00:15:21,040 --> 00:15:23,850 respect to the number of atoms that form the close pack is 2 n for the 518 00:15:23,850 --> 00:15:23,860 the close pack is 2 n for the 519 00:15:23,860 --> 00:15:26,850 the close pack is 2 n for the tetrahedral and for the octahedral case 520 00:15:26,850 --> 00:15:26,860 tetrahedral and for the octahedral case 521 00:15:26,860 --> 00:15:30,390 tetrahedral and for the octahedral case now the other structure I guess 522 00:15:30,390 --> 00:15:30,400 now the other structure I guess 523 00:15:30,400 --> 00:15:33,500 now the other structure I guess character property of the close packing 524 00:15:33,500 --> 00:15:33,510 character property of the close packing 525 00:15:33,510 --> 00:15:39,600 character property of the close packing if I take one atom here somewhere and 526 00:15:39,600 --> 00:15:39,610 if I take one atom here somewhere and 527 00:15:39,610 --> 00:15:44,550 if I take one atom here somewhere and then find out how many other atoms are 528 00:15:44,550 --> 00:15:44,560 then find out how many other atoms are 529 00:15:44,560 --> 00:15:48,600 then find out how many other atoms are in the closest neighborhood or if I put 530 00:15:48,600 --> 00:15:48,610 in the closest neighborhood or if I put 531 00:15:48,610 --> 00:15:49,079 in the closest neighborhood or if I put it 532 00:15:49,079 --> 00:15:49,089 it 533 00:15:49,089 --> 00:15:51,150 it different way how many atoms are 534 00:15:51,150 --> 00:15:51,160 different way how many atoms are 535 00:15:51,160 --> 00:15:54,780 different way how many atoms are touching to one atom in the close-packed 536 00:15:54,780 --> 00:15:54,790 touching to one atom in the close-packed 537 00:15:54,790 --> 00:15:57,119 touching to one atom in the close-packed structures and we will find out that 538 00:15:57,119 --> 00:15:57,129 structures and we will find out that 539 00:15:57,129 --> 00:16:02,429 structures and we will find out that there are 12 actually atoms and now if 540 00:16:02,429 --> 00:16:02,439 there are 12 actually atoms and now if 541 00:16:02,439 --> 00:16:05,369 there are 12 actually atoms and now if you simply consider an atom here or a 542 00:16:05,369 --> 00:16:05,379 you simply consider an atom here or a 543 00:16:05,379 --> 00:16:07,650 you simply consider an atom here or a sphere in the middle right here there 544 00:16:07,650 --> 00:16:07,660 sphere in the middle right here there 545 00:16:07,660 --> 00:16:10,139 sphere in the middle right here there will be six of those around in the same 546 00:16:10,139 --> 00:16:10,149 will be six of those around in the same 547 00:16:10,149 --> 00:16:13,079 will be six of those around in the same layer and there will be three on the top 548 00:16:13,079 --> 00:16:13,089 layer and there will be three on the top 549 00:16:13,089 --> 00:16:16,860 layer and there will be three on the top and three in the bottom so one sphere 550 00:16:16,860 --> 00:16:16,870 and three in the bottom so one sphere 551 00:16:16,870 --> 00:16:21,210 and three in the bottom so one sphere actually is touching twelve spheres in a 552 00:16:21,210 --> 00:16:21,220 actually is touching twelve spheres in a 553 00:16:21,220 --> 00:16:24,600 actually is touching twelve spheres in a close-packed structures and this number 554 00:16:24,600 --> 00:16:24,610 close-packed structures and this number 555 00:16:24,610 --> 00:16:27,210 close-packed structures and this number 12 is simply called the coordination 556 00:16:27,210 --> 00:16:27,220 12 is simply called the coordination 557 00:16:27,220 --> 00:16:30,449 12 is simply called the coordination number of that atom coordination number 558 00:16:30,449 --> 00:16:30,459 number of that atom coordination number 559 00:16:30,459 --> 00:16:32,400 number of that atom coordination number of atom so when we say coordination 560 00:16:32,400 --> 00:16:32,410 of atom so when we say coordination 561 00:16:32,410 --> 00:16:34,230 of atom so when we say coordination number it is the number of atoms that 562 00:16:34,230 --> 00:16:34,240 number it is the number of atoms that 563 00:16:34,240 --> 00:16:39,239 number it is the number of atoms that actually touching to that atom or I 564 00:16:39,239 --> 00:16:39,249 actually touching to that atom or I 565 00:16:39,249 --> 00:16:42,059 actually touching to that atom or I should say the number of atoms which are 566 00:16:42,059 --> 00:16:42,069 should say the number of atoms which are 567 00:16:42,069 --> 00:16:44,970 should say the number of atoms which are fine in the closest neighborhood of that 568 00:16:44,970 --> 00:16:44,980 fine in the closest neighborhood of that 569 00:16:44,980 --> 00:16:47,639 fine in the closest neighborhood of that atom so in both cases coordination 570 00:16:47,639 --> 00:16:47,649 atom so in both cases coordination 571 00:16:47,649 --> 00:16:51,480 atom so in both cases coordination number of the atoms in fact in HCP or 572 00:16:51,480 --> 00:16:51,490 number of the atoms in fact in HCP or 573 00:16:51,490 --> 00:16:54,960 number of the atoms in fact in HCP or CCP is 12 and 12 is almost the highest 574 00:16:54,960 --> 00:16:54,970 CCP is 12 and 12 is almost the highest 575 00:16:54,970 --> 00:16:57,059 CCP is 12 and 12 is almost the highest coordination number heis coordination 576 00:16:57,059 --> 00:16:57,069 coordination number heis coordination 577 00:16:57,069 --> 00:17:00,239 coordination number heis coordination number this also indicates that we pack 578 00:17:00,239 --> 00:17:00,249 number this also indicates that we pack 579 00:17:00,249 --> 00:17:03,600 number this also indicates that we pack those atoms as close as possible in a 580 00:17:03,600 --> 00:17:03,610 those atoms as close as possible in a 581 00:17:03,610 --> 00:17:06,919 those atoms as close as possible in a given volume in a given volume okay so 582 00:17:06,919 --> 00:17:06,929 given volume in a given volume okay so 583 00:17:06,929 --> 00:17:11,149 given volume in a given volume okay so for example if somebody tells you that 584 00:17:11,149 --> 00:17:11,159 for example if somebody tells you that 585 00:17:11,159 --> 00:17:17,069 for example if somebody tells you that the unit cell of a metal atom solid 586 00:17:17,069 --> 00:17:17,079 the unit cell of a metal atom solid 587 00:17:17,079 --> 00:17:22,429 the unit cell of a metal atom solid metal atom is body centered cubic and 588 00:17:22,429 --> 00:17:22,439 metal atom is body centered cubic and 589 00:17:22,439 --> 00:17:26,449 metal atom is body centered cubic and ask you is this a closed pack structure 590 00:17:26,449 --> 00:17:26,459 ask you is this a closed pack structure 591 00:17:26,459 --> 00:17:32,190 ask you is this a closed pack structure is it a closed pack structure if the 592 00:17:32,190 --> 00:17:32,200 is it a closed pack structure if the 593 00:17:32,200 --> 00:17:35,370 is it a closed pack structure if the unit cell off the metal is body centered 594 00:17:35,370 --> 00:17:35,380 unit cell off the metal is body centered 595 00:17:35,380 --> 00:17:39,779 unit cell off the metal is body centered cubic and the answer will be no why 596 00:17:39,779 --> 00:17:39,789 cubic and the answer will be no why 597 00:17:39,789 --> 00:17:44,159 cubic and the answer will be no why because close packed structures the unit 598 00:17:44,159 --> 00:17:44,169 because close packed structures the unit 599 00:17:44,169 --> 00:17:48,320 because close packed structures the unit cell has to be face centered or 600 00:17:48,320 --> 00:17:48,330 cell has to be face centered or 601 00:17:48,330 --> 00:17:50,490 cell has to be face centered or hexagonal inner-self 602 00:17:50,490 --> 00:17:50,500 hexagonal inner-self 603 00:17:50,500 --> 00:17:53,730 hexagonal inner-self right face centered or exactly if the 604 00:17:53,730 --> 00:17:53,740 right face centered or exactly if the 605 00:17:53,740 --> 00:17:57,480 right face centered or exactly if the structure if the unit cell actually is 606 00:17:57,480 --> 00:17:57,490 structure if the unit cell actually is 607 00:17:57,490 --> 00:18:01,080 structure if the unit cell actually is not cubic face-centered cubic or 608 00:18:01,080 --> 00:18:01,090 not cubic face-centered cubic or 609 00:18:01,090 --> 00:18:02,940 not cubic face-centered cubic or hexagonal that 610 00:18:02,940 --> 00:18:02,950 hexagonal that 611 00:18:02,950 --> 00:18:05,790 hexagonal that that structure is not closed pack 612 00:18:05,790 --> 00:18:05,800 that structure is not closed pack 613 00:18:05,800 --> 00:18:08,070 that structure is not closed pack structure closed pack structure so we 614 00:18:08,070 --> 00:18:08,080 structure closed pack structure so we 615 00:18:08,080 --> 00:18:10,710 structure closed pack structure so we have to keep that in mind again now by 616 00:18:10,710 --> 00:18:10,720 have to keep that in mind again now by 617 00:18:10,720 --> 00:18:16,400 have to keep that in mind again now by using actually these unit cells in fact 618 00:18:16,400 --> 00:18:16,410 using actually these unit cells in fact 619 00:18:16,410 --> 00:18:19,500 using actually these unit cells in fact let's say these three unit cells last 620 00:18:19,500 --> 00:18:19,510 let's say these three unit cells last 621 00:18:19,510 --> 00:18:25,640 let's say these three unit cells last time remember we calculated the percent 622 00:18:25,640 --> 00:18:25,650 time remember we calculated the percent 623 00:18:25,650 --> 00:18:30,150 time remember we calculated the percent efficiency packing or efficiency of 624 00:18:30,150 --> 00:18:30,160 efficiency packing or efficiency of 625 00:18:30,160 --> 00:18:34,730 efficiency packing or efficiency of packing in fact in these three unit cell 626 00:18:34,730 --> 00:18:34,740 packing in fact in these three unit cell 627 00:18:34,740 --> 00:18:37,470 packing in fact in these three unit cell structures or unit cell lettuces in fact 628 00:18:37,470 --> 00:18:37,480 structures or unit cell lettuces in fact 629 00:18:37,480 --> 00:18:41,760 structures or unit cell lettuces in fact and we find out that the packing 630 00:18:41,760 --> 00:18:41,770 and we find out that the packing 631 00:18:41,770 --> 00:18:44,490 and we find out that the packing efficiency in the primitive unit cell 632 00:18:44,490 --> 00:18:44,500 efficiency in the primitive unit cell 633 00:18:44,500 --> 00:18:48,990 efficiency in the primitive unit cell cubic unit cell calculated to be 52% 634 00:18:48,990 --> 00:18:49,000 cubic unit cell calculated to be 52% 635 00:18:49,000 --> 00:18:51,660 cubic unit cell calculated to be 52% what does that means that means that in 636 00:18:51,660 --> 00:18:51,670 what does that means that means that in 637 00:18:51,670 --> 00:18:55,920 what does that means that means that in the three dimensional lattice which have 638 00:18:55,920 --> 00:18:55,930 the three dimensional lattice which have 639 00:18:55,930 --> 00:19:01,290 the three dimensional lattice which have that unit cell 52 percent of the space 640 00:19:01,290 --> 00:19:01,300 that unit cell 52 percent of the space 641 00:19:01,300 --> 00:19:06,930 that unit cell 52 percent of the space is full and 48 percent is empty right 642 00:19:06,930 --> 00:19:06,940 is full and 48 percent is empty right 643 00:19:06,940 --> 00:19:08,790 is full and 48 percent is empty right and what is the empty means that means 644 00:19:08,790 --> 00:19:08,800 and what is the empty means that means 645 00:19:08,800 --> 00:19:11,310 and what is the empty means that means those are they simply the spaces between 646 00:19:11,310 --> 00:19:11,320 those are they simply the spaces between 647 00:19:11,320 --> 00:19:14,010 those are they simply the spaces between the spheres you can think about that 648 00:19:14,010 --> 00:19:14,020 the spheres you can think about that 649 00:19:14,020 --> 00:19:15,660 the spheres you can think about that between the same size spheres 650 00:19:15,660 --> 00:19:15,670 between the same size spheres 651 00:19:15,670 --> 00:19:18,960 between the same size spheres now when we calculated this one we find 652 00:19:18,960 --> 00:19:18,970 now when we calculated this one we find 653 00:19:18,970 --> 00:19:22,820 now when we calculated this one we find out it is 68% for the body center and 654 00:19:22,820 --> 00:19:22,830 out it is 68% for the body center and 655 00:19:22,830 --> 00:19:25,620 out it is 68% for the body center and for this one which is the face center we 656 00:19:25,620 --> 00:19:25,630 for this one which is the face center we 657 00:19:25,630 --> 00:19:29,130 for this one which is the face center we calculated it to be 74% so you see again 658 00:19:29,130 --> 00:19:29,140 calculated it to be 74% so you see again 659 00:19:29,140 --> 00:19:32,220 calculated it to be 74% so you see again this one if the unit cells face centered 660 00:19:32,220 --> 00:19:32,230 this one if the unit cells face centered 661 00:19:32,230 --> 00:19:34,590 this one if the unit cells face centered cubic that means that that lattice 662 00:19:34,590 --> 00:19:34,600 cubic that means that that lattice 663 00:19:34,600 --> 00:19:36,990 cubic that means that that lattice structure is closed packing lattice that 664 00:19:36,990 --> 00:19:37,000 structure is closed packing lattice that 665 00:19:37,000 --> 00:19:40,710 structure is closed packing lattice that means we will have the highest packing 666 00:19:40,710 --> 00:19:40,720 means we will have the highest packing 667 00:19:40,720 --> 00:19:43,800 means we will have the highest packing efficiency and we have actually 74% 668 00:19:43,800 --> 00:19:43,810 efficiency and we have actually 74% 669 00:19:43,810 --> 00:19:45,420 efficiency and we have actually 74% which is the highest packing 670 00:19:45,420 --> 00:19:45,430 which is the highest packing 671 00:19:45,430 --> 00:19:50,840 which is the highest packing efficiencies now let me before I go I 672 00:19:50,840 --> 00:19:50,850 efficiencies now let me before I go I 673 00:19:50,850 --> 00:19:54,990 efficiencies now let me before I go I will solve you another problem example 674 00:19:54,990 --> 00:19:55,000 will solve you another problem example 675 00:19:55,000 --> 00:19:59,220 will solve you another problem example problem how we use these unit cells and 676 00:19:59,220 --> 00:19:59,230 problem how we use these unit cells and 677 00:19:59,230 --> 00:20:03,240 problem how we use these unit cells and unit cells dimension to calculate the 678 00:20:03,240 --> 00:20:03,250 unit cells dimension to calculate the 679 00:20:03,250 --> 00:20:05,910 unit cells dimension to calculate the density for example of the solids or if 680 00:20:05,910 --> 00:20:05,920 density for example of the solids or if 681 00:20:05,920 --> 00:20:09,120 density for example of the solids or if you know the density to calculate the 682 00:20:09,120 --> 00:20:09,130 you know the density to calculate the 683 00:20:09,130 --> 00:20:12,330 you know the density to calculate the edge of the unit cell or if you know the 684 00:20:12,330 --> 00:20:12,340 edge of the unit cell or if you know the 685 00:20:12,340 --> 00:20:13,950 edge of the unit cell or if you know the edge of the unit cell we can calculate 686 00:20:13,950 --> 00:20:13,960 edge of the unit cell we can calculate 687 00:20:13,960 --> 00:20:16,470 edge of the unit cell we can calculate the radius of the 688 00:20:16,470 --> 00:20:16,480 the radius of the 689 00:20:16,480 --> 00:20:18,870 the radius of the atoms actually radiate off the atoms now 690 00:20:18,870 --> 00:20:18,880 atoms actually radiate off the atoms now 691 00:20:18,880 --> 00:20:22,560 atoms actually radiate off the atoms now let me just go through this example 692 00:20:22,560 --> 00:20:22,570 let me just go through this example 693 00:20:22,570 --> 00:20:25,350 let me just go through this example actual problem at the end of the chapter 694 00:20:25,350 --> 00:20:25,360 actual problem at the end of the chapter 695 00:20:25,360 --> 00:20:31,380 actual problem at the end of the chapter and this is problem 12:35 from the book 696 00:20:31,380 --> 00:20:31,390 and this is problem 12:35 from the book 697 00:20:31,390 --> 00:20:39,539 and this is problem 12:35 from the book chapter 12 problem 35 now this simply 698 00:20:39,539 --> 00:20:39,549 chapter 12 problem 35 now this simply 699 00:20:39,549 --> 00:20:43,250 chapter 12 problem 35 now this simply says that we have aluminum solid 700 00:20:43,250 --> 00:20:43,260 says that we have aluminum solid 701 00:20:43,260 --> 00:20:46,880 says that we have aluminum solid aluminum this is a metal right solid and 702 00:20:46,880 --> 00:20:46,890 aluminum this is a metal right solid and 703 00:20:46,890 --> 00:20:52,909 aluminum this is a metal right solid and it has face centered cubic unit cell so 704 00:20:52,909 --> 00:20:52,919 it has face centered cubic unit cell so 705 00:20:52,919 --> 00:20:59,430 it has face centered cubic unit cell so phase centered cubic unit cell this is 706 00:20:59,430 --> 00:20:59,440 phase centered cubic unit cell this is 707 00:20:59,440 --> 00:21:08,280 phase centered cubic unit cell this is the information given now the first 708 00:21:08,280 --> 00:21:08,290 the information given now the first 709 00:21:08,290 --> 00:21:13,409 the information given now the first question it says how many aluminum atoms 710 00:21:13,409 --> 00:21:13,419 question it says how many aluminum atoms 711 00:21:13,419 --> 00:21:27,000 question it says how many aluminum atoms are present in one unit cell 712 00:21:27,000 --> 00:21:27,010 713 00:21:27,010 --> 00:21:32,860 so we have simply corners here and also 714 00:21:32,860 --> 00:21:32,870 so we have simply corners here and also 715 00:21:32,870 --> 00:21:36,850 so we have simply corners here and also at the middle of the faces so how many 716 00:21:36,850 --> 00:21:36,860 at the middle of the faces so how many 717 00:21:36,860 --> 00:21:41,170 at the middle of the faces so how many you know how many aluminum atoms belongs 718 00:21:41,170 --> 00:21:41,180 you know how many aluminum atoms belongs 719 00:21:41,180 --> 00:21:44,860 you know how many aluminum atoms belongs to one unit cell in this structure it 720 00:21:44,860 --> 00:21:44,870 to one unit cell in this structure it 721 00:21:44,870 --> 00:21:46,930 to one unit cell in this structure it would be actually this right right there 722 00:21:46,930 --> 00:21:46,940 would be actually this right right there 723 00:21:46,940 --> 00:21:50,830 would be actually this right right there so it is four so the answer to that for 724 00:21:50,830 --> 00:21:50,840 so it is four so the answer to that for 725 00:21:50,840 --> 00:21:53,980 so it is four so the answer to that for aluminum atoms in one unit cell let's 726 00:21:53,980 --> 00:21:53,990 aluminum atoms in one unit cell let's 727 00:21:53,990 --> 00:22:09,000 aluminum atoms in one unit cell let's say four aluminum atoms in one unit cell 728 00:22:09,000 --> 00:22:09,010 729 00:22:09,010 --> 00:22:14,290 okay in the second part it says what is 730 00:22:14,290 --> 00:22:14,300 okay in the second part it says what is 731 00:22:14,300 --> 00:22:21,630 okay in the second part it says what is the coordination number of aluminum atom 732 00:22:21,630 --> 00:22:21,640 733 00:22:21,640 --> 00:22:24,670 now again remember coordination number 734 00:22:24,670 --> 00:22:24,680 now again remember coordination number 735 00:22:24,680 --> 00:22:28,630 now again remember coordination number is the number of atoms that are touching 736 00:22:28,630 --> 00:22:28,640 is the number of atoms that are touching 737 00:22:28,640 --> 00:22:32,290 is the number of atoms that are touching in contact with that so for the 738 00:22:32,290 --> 00:22:32,300 in contact with that so for the 739 00:22:32,300 --> 00:22:34,660 in contact with that so for the close-packed structure this this since 740 00:22:34,660 --> 00:22:34,670 close-packed structure this this since 741 00:22:34,670 --> 00:22:37,450 close-packed structure this this since this is a face centered cubic unit cell 742 00:22:37,450 --> 00:22:37,460 this is a face centered cubic unit cell 743 00:22:37,460 --> 00:22:40,360 this is a face centered cubic unit cell that means that the aluminum lattice is 744 00:22:40,360 --> 00:22:40,370 that means that the aluminum lattice is 745 00:22:40,370 --> 00:22:43,390 that means that the aluminum lattice is close packed cubic close pack lattice 746 00:22:43,390 --> 00:22:43,400 close packed cubic close pack lattice 747 00:22:43,400 --> 00:22:45,790 close packed cubic close pack lattice right so what does that means that means 748 00:22:45,790 --> 00:22:45,800 right so what does that means that means 749 00:22:45,800 --> 00:22:48,040 right so what does that means that means that the number of atoms that touch in 750 00:22:48,040 --> 00:22:48,050 that the number of atoms that touch in 751 00:22:48,050 --> 00:22:51,490 that the number of atoms that touch in one atom or coordination number is 12 12 752 00:22:51,490 --> 00:22:51,500 one atom or coordination number is 12 12 753 00:22:51,500 --> 00:22:54,250 one atom or coordination number is 12 12 is actually the maximum as I said 12 so 754 00:22:54,250 --> 00:22:54,260 is actually the maximum as I said 12 so 755 00:22:54,260 --> 00:22:59,400 is actually the maximum as I said 12 so as here is coordination number 756 00:22:59,400 --> 00:22:59,410 757 00:22:59,410 --> 00:23:09,390 coordination number of aluminum atom 758 00:23:09,390 --> 00:23:09,400 759 00:23:09,400 --> 00:23:16,720 aluminum atom is 12 and then the third 760 00:23:16,720 --> 00:23:16,730 aluminum atom is 12 and then the third 761 00:23:16,730 --> 00:23:23,740 aluminum atom is 12 and then the third it says can you calculate the density of 762 00:23:23,740 --> 00:23:23,750 it says can you calculate the density of 763 00:23:23,750 --> 00:23:29,290 it says can you calculate the density of aluminum metal provided that you're 764 00:23:29,290 --> 00:23:29,300 aluminum metal provided that you're 765 00:23:29,300 --> 00:23:34,030 aluminum metal provided that you're given the radius of aluminum and you're 766 00:23:34,030 --> 00:23:34,040 given the radius of aluminum and you're 767 00:23:34,040 --> 00:23:38,369 given the radius of aluminum and you're also given the atomic mass 768 00:23:38,369 --> 00:23:38,379 also given the atomic mass 769 00:23:38,379 --> 00:23:45,129 also given the atomic mass of aluminum right so aluminum let's say 770 00:23:45,129 --> 00:23:45,139 of aluminum right so aluminum let's say 771 00:23:45,139 --> 00:23:50,169 of aluminum right so aluminum let's say our aluminum the radius of aluminum is 772 00:23:50,169 --> 00:23:50,179 our aluminum the radius of aluminum is 773 00:23:50,179 --> 00:23:56,199 our aluminum the radius of aluminum is given as 1 point 43 angstrom and the 774 00:23:56,199 --> 00:23:56,209 given as 1 point 43 angstrom and the 775 00:23:56,209 --> 00:24:01,029 given as 1 point 43 angstrom and the molar mass of aluminum is given as let's 776 00:24:01,029 --> 00:24:01,039 molar mass of aluminum is given as let's 777 00:24:01,039 --> 00:24:10,889 molar mass of aluminum is given as let's say molar mass aluminum of aluminum is 778 00:24:10,889 --> 00:24:10,899 say molar mass aluminum of aluminum is 779 00:24:10,899 --> 00:24:14,169 say molar mass aluminum of aluminum is this is again from periodic table right 780 00:24:14,169 --> 00:24:14,179 this is again from periodic table right 781 00:24:14,179 --> 00:24:16,659 this is again from periodic table right create a table you just look at the 782 00:24:16,659 --> 00:24:16,669 create a table you just look at the 783 00:24:16,669 --> 00:24:23,919 create a table you just look at the atomic weight and 26 point 98 grams per 784 00:24:23,919 --> 00:24:23,929 atomic weight and 26 point 98 grams per 785 00:24:23,929 --> 00:24:30,249 atomic weight and 26 point 98 grams per mole okay these are given and now we're 786 00:24:30,249 --> 00:24:30,259 mole okay these are given and now we're 787 00:24:30,259 --> 00:24:34,029 mole okay these are given and now we're asked to calculate what is the density 788 00:24:34,029 --> 00:24:34,039 asked to calculate what is the density 789 00:24:34,039 --> 00:24:46,139 asked to calculate what is the density see here what is the density of aluminum 790 00:24:46,139 --> 00:24:46,149 see here what is the density of aluminum 791 00:24:46,149 --> 00:24:50,979 see here what is the density of aluminum solid right how again these type of 792 00:24:50,979 --> 00:24:50,989 solid right how again these type of 793 00:24:50,989 --> 00:24:55,119 solid right how again these type of problems are very common usually appears 794 00:24:55,119 --> 00:24:55,129 problems are very common usually appears 795 00:24:55,129 --> 00:25:01,269 problems are very common usually appears in the exam how can we calculate it once 796 00:25:01,269 --> 00:25:01,279 in the exam how can we calculate it once 797 00:25:01,279 --> 00:25:05,919 in the exam how can we calculate it once you learn how to do that for a problem 798 00:25:05,919 --> 00:25:05,929 you learn how to do that for a problem 799 00:25:05,929 --> 00:25:07,959 you learn how to do that for a problem like this you can simply apply it to all 800 00:25:07,959 --> 00:25:07,969 like this you can simply apply it to all 801 00:25:07,969 --> 00:25:13,959 like this you can simply apply it to all others now what we simply need here is 802 00:25:13,959 --> 00:25:13,969 others now what we simply need here is 803 00:25:13,969 --> 00:25:17,049 others now what we simply need here is this we will calculate density of 804 00:25:17,049 --> 00:25:17,059 this we will calculate density of 805 00:25:17,059 --> 00:25:23,619 this we will calculate density of aluminum to calculate density I have to 806 00:25:23,619 --> 00:25:23,629 aluminum to calculate density I have to 807 00:25:23,629 --> 00:25:28,479 aluminum to calculate density I have to know the mass of a given volume of the 808 00:25:28,479 --> 00:25:28,489 know the mass of a given volume of the 809 00:25:28,489 --> 00:25:31,509 know the mass of a given volume of the substance right so that means that I 810 00:25:31,509 --> 00:25:31,519 substance right so that means that I 811 00:25:31,519 --> 00:25:35,529 substance right so that means that I should simply have a mass let's say here 812 00:25:35,529 --> 00:25:35,539 should simply have a mass let's say here 813 00:25:35,539 --> 00:25:40,319 should simply have a mass let's say here mass divided by the volume that means 814 00:25:40,319 --> 00:25:40,329 mass divided by the volume that means 815 00:25:40,329 --> 00:25:42,999 mass divided by the volume that means this is the volume of this mass and that 816 00:25:42,999 --> 00:25:43,009 this is the volume of this mass and that 817 00:25:43,009 --> 00:25:45,399 this is the volume of this mass and that that will give you simply the density 818 00:25:45,399 --> 00:25:45,409 that will give you simply the density 819 00:25:45,409 --> 00:25:50,649 that will give you simply the density now what mass I should take in this case 820 00:25:50,649 --> 00:25:50,659 now what mass I should take in this case 821 00:25:50,659 --> 00:25:52,330 now what mass I should take in this case and what volume I should take in this 822 00:25:52,330 --> 00:25:52,340 and what volume I should take in this 823 00:25:52,340 --> 00:25:56,190 and what volume I should take in this case now the mass that I should take is 824 00:25:56,190 --> 00:25:56,200 case now the mass that I should take is 825 00:25:56,200 --> 00:26:01,690 case now the mass that I should take is the number of aluminum atoms in one unit 826 00:26:01,690 --> 00:26:01,700 the number of aluminum atoms in one unit 827 00:26:01,700 --> 00:26:12,009 the number of aluminum atoms in one unit cell right and the volume should be the 828 00:26:12,009 --> 00:26:12,019 cell right and the volume should be the 829 00:26:12,019 --> 00:26:15,749 cell right and the volume should be the volume of the unit cell 830 00:26:15,749 --> 00:26:15,759 831 00:26:15,759 --> 00:26:19,149 right the volume after yourself now how 832 00:26:19,149 --> 00:26:19,159 right the volume after yourself now how 833 00:26:19,159 --> 00:26:22,599 right the volume after yourself now how can I find the volume of the unit cell 834 00:26:22,599 --> 00:26:22,609 can I find the volume of the unit cell 835 00:26:22,609 --> 00:26:45,580 can I find the volume of the unit cell let's see actually the mass let's say 836 00:26:45,580 --> 00:26:45,590 let's see actually the mass let's say 837 00:26:45,590 --> 00:26:53,799 let's see actually the mass let's say over here the mass of unit cell will be 838 00:26:53,799 --> 00:26:53,809 over here the mass of unit cell will be 839 00:26:53,809 --> 00:26:59,409 over here the mass of unit cell will be equal to four times the mass of aluminum 840 00:26:59,409 --> 00:26:59,419 equal to four times the mass of aluminum 841 00:26:59,419 --> 00:27:01,779 equal to four times the mass of aluminum atoms right why because it's face 842 00:27:01,779 --> 00:27:01,789 atoms right why because it's face 843 00:27:01,789 --> 00:27:04,960 atoms right why because it's face centered cubic unit cell in phase 844 00:27:04,960 --> 00:27:04,970 centered cubic unit cell in phase 845 00:27:04,970 --> 00:27:08,200 centered cubic unit cell in phase centered cubic unit cell for atoms 846 00:27:08,200 --> 00:27:08,210 centered cubic unit cell for atoms 847 00:27:08,210 --> 00:27:11,049 centered cubic unit cell for atoms belongs to one unit cell so that means 848 00:27:11,049 --> 00:27:11,059 belongs to one unit cell so that means 849 00:27:11,059 --> 00:27:14,619 belongs to one unit cell so that means that this will be multiplied by the mass 850 00:27:14,619 --> 00:27:14,629 that this will be multiplied by the mass 851 00:27:14,629 --> 00:27:20,049 that this will be multiplied by the mass of one aluminum atom now the mass of one 852 00:27:20,049 --> 00:27:20,059 of one aluminum atom now the mass of one 853 00:27:20,059 --> 00:27:22,749 of one aluminum atom now the mass of one aluminum atom in grams one aluminum atom 854 00:27:22,749 --> 00:27:22,759 aluminum atom in grams one aluminum atom 855 00:27:22,759 --> 00:27:25,570 aluminum atom in grams one aluminum atom in grams would be equal to the molar 856 00:27:25,570 --> 00:27:25,580 in grams would be equal to the molar 857 00:27:25,580 --> 00:27:32,769 in grams would be equal to the molar mass which is simply 2698 2698 divided 858 00:27:32,769 --> 00:27:32,779 mass which is simply 2698 2698 divided 859 00:27:32,779 --> 00:27:36,339 mass which is simply 2698 2698 divided by what Avogadro's number right 860 00:27:36,339 --> 00:27:36,349 by what Avogadro's number right 861 00:27:36,349 --> 00:27:40,049 by what Avogadro's number right Avogadro's number 6.02 times 10 to the 862 00:27:40,049 --> 00:27:40,059 Avogadro's number 6.02 times 10 to the 863 00:27:40,059 --> 00:27:44,859 Avogadro's number 6.02 times 10 to the 23 and if you simply work that out this 864 00:27:44,859 --> 00:27:44,869 23 and if you simply work that out this 865 00:27:44,869 --> 00:27:48,460 23 and if you simply work that out this will give you the mass of the unit cell 866 00:27:48,460 --> 00:27:48,470 will give you the mass of the unit cell 867 00:27:48,470 --> 00:27:50,710 will give you the mass of the unit cell the mass of the unit cell and that will 868 00:27:50,710 --> 00:27:50,720 the mass of the unit cell and that will 869 00:27:50,720 --> 00:27:53,499 the mass of the unit cell and that will be again if I work it out it will be one 870 00:27:53,499 --> 00:27:53,509 be again if I work it out it will be one 871 00:27:53,509 --> 00:27:57,279 be again if I work it out it will be one point seven nine I did work it out times 872 00:27:57,279 --> 00:27:57,289 point seven nine I did work it out times 873 00:27:57,289 --> 00:28:01,100 point seven nine I did work it out times 10 to the minus 22 in grams 874 00:28:01,100 --> 00:28:01,110 10 to the minus 22 in grams 875 00:28:01,110 --> 00:28:02,900 10 to the minus 22 in grams it has to be in grams because this is 876 00:28:02,900 --> 00:28:02,910 it has to be in grams because this is 877 00:28:02,910 --> 00:28:05,720 it has to be in grams because this is gram per mole this is number of atoms 878 00:28:05,720 --> 00:28:05,730 gram per mole this is number of atoms 879 00:28:05,730 --> 00:28:08,299 gram per mole this is number of atoms per mole so that cancels out that 880 00:28:08,299 --> 00:28:08,309 per mole so that cancels out that 881 00:28:08,309 --> 00:28:10,850 per mole so that cancels out that becomes the grams per four atoms 882 00:28:10,850 --> 00:28:10,860 becomes the grams per four atoms 883 00:28:10,860 --> 00:28:13,940 becomes the grams per four atoms actually this becomes the mass of the 884 00:28:13,940 --> 00:28:13,950 actually this becomes the mass of the 885 00:28:13,950 --> 00:28:17,990 actually this becomes the mass of the unit cell now how about the volume of 886 00:28:17,990 --> 00:28:18,000 unit cell now how about the volume of 887 00:28:18,000 --> 00:28:20,690 unit cell now how about the volume of the unit cell now I can find out the 888 00:28:20,690 --> 00:28:20,700 the unit cell now I can find out the 889 00:28:20,700 --> 00:28:23,000 the unit cell now I can find out the volume of the unit cell again knowing 890 00:28:23,000 --> 00:28:23,010 volume of the unit cell again knowing 891 00:28:23,010 --> 00:28:25,760 volume of the unit cell again knowing the unit cell structure it is face 892 00:28:25,760 --> 00:28:25,770 the unit cell structure it is face 893 00:28:25,770 --> 00:28:28,340 the unit cell structure it is face centered so if I simply take one face 894 00:28:28,340 --> 00:28:28,350 centered so if I simply take one face 895 00:28:28,350 --> 00:28:33,350 centered so if I simply take one face off the unit cell it's a cubic unit cell 896 00:28:33,350 --> 00:28:33,360 off the unit cell it's a cubic unit cell 897 00:28:33,360 --> 00:28:37,280 off the unit cell it's a cubic unit cell right and I know that face centered unit 898 00:28:37,280 --> 00:28:37,290 right and I know that face centered unit 899 00:28:37,290 --> 00:28:42,560 right and I know that face centered unit cells I have simply one atom at the 900 00:28:42,560 --> 00:28:42,570 cells I have simply one atom at the 901 00:28:42,570 --> 00:28:46,280 cells I have simply one atom at the center and now all the others are simply 902 00:28:46,280 --> 00:28:46,290 center and now all the others are simply 903 00:28:46,290 --> 00:28:48,560 center and now all the others are simply touching to this they're all the same 904 00:28:48,560 --> 00:28:48,570 touching to this they're all the same 905 00:28:48,570 --> 00:28:54,260 touching to this they're all the same size like this now this is actually the 906 00:28:54,260 --> 00:28:54,270 size like this now this is actually the 907 00:28:54,270 --> 00:28:57,320 size like this now this is actually the edge of the unit cell let's call that a 908 00:28:57,320 --> 00:28:57,330 edge of the unit cell let's call that a 909 00:28:57,330 --> 00:29:05,750 edge of the unit cell let's call that a a is edge off the unit cell right edge 910 00:29:05,750 --> 00:29:05,760 a is edge off the unit cell right edge 911 00:29:05,760 --> 00:29:07,850 a is edge off the unit cell right edge of the unit cell so if I can calculate 912 00:29:07,850 --> 00:29:07,860 of the unit cell so if I can calculate 913 00:29:07,860 --> 00:29:11,090 of the unit cell so if I can calculate that I will calculate the volume because 914 00:29:11,090 --> 00:29:11,100 that I will calculate the volume because 915 00:29:11,100 --> 00:29:12,950 that I will calculate the volume because a to the cube will be the volume of the 916 00:29:12,950 --> 00:29:12,960 a to the cube will be the volume of the 917 00:29:12,960 --> 00:29:15,049 a to the cube will be the volume of the unit cell now how can I calculate the 918 00:29:15,049 --> 00:29:15,059 unit cell now how can I calculate the 919 00:29:15,059 --> 00:29:20,260 unit cell now how can I calculate the Valley a actually from the radius of the 920 00:29:20,260 --> 00:29:20,270 Valley a actually from the radius of the 921 00:29:20,270 --> 00:29:23,570 Valley a actually from the radius of the atoms the radius of the atoms are simply 922 00:29:23,570 --> 00:29:23,580 atoms the radius of the atoms are simply 923 00:29:23,580 --> 00:29:28,580 atoms the radius of the atoms are simply 1.48 and we will consider this right 924 00:29:28,580 --> 00:29:28,590 1.48 and we will consider this right 925 00:29:28,590 --> 00:29:34,669 1.48 and we will consider this right angle triangle here and this part here 926 00:29:34,669 --> 00:29:34,679 angle triangle here and this part here 927 00:29:34,679 --> 00:29:38,060 angle triangle here and this part here is the phase diagonal and that phase 928 00:29:38,060 --> 00:29:38,070 is the phase diagonal and that phase 929 00:29:38,070 --> 00:29:45,250 is the phase diagonal and that phase diagonal is equals to 4 R right and then 930 00:29:45,250 --> 00:29:45,260 diagonal is equals to 4 R right and then 931 00:29:45,260 --> 00:29:49,820 diagonal is equals to 4 R right and then this is the edge of the unit cell so I 932 00:29:49,820 --> 00:29:49,830 this is the edge of the unit cell so I 933 00:29:49,830 --> 00:29:52,430 this is the edge of the unit cell so I can simply write down this is phase 934 00:29:52,430 --> 00:29:52,440 can simply write down this is phase 935 00:29:52,440 --> 00:29:56,120 can simply write down this is phase diagonal this d square would be equal to 936 00:29:56,120 --> 00:29:56,130 diagonal this d square would be equal to 937 00:29:56,130 --> 00:29:59,510 diagonal this d square would be equal to a squared plus a squared that means a 938 00:29:59,510 --> 00:29:59,520 a squared plus a squared that means a 939 00:29:59,520 --> 00:30:02,390 a squared plus a squared that means a squared plus another way square that's 940 00:30:02,390 --> 00:30:02,400 squared plus another way square that's 941 00:30:02,400 --> 00:30:05,960 squared plus another way square that's equal to 2a squared now from here if you 942 00:30:05,960 --> 00:30:05,970 equal to 2a squared now from here if you 943 00:30:05,970 --> 00:30:11,780 equal to 2a squared now from here if you replace the D by R and make it as for R 944 00:30:11,780 --> 00:30:11,790 replace the D by R and make it as for R 945 00:30:11,790 --> 00:30:13,280 replace the D by R and make it as for R to the square 946 00:30:13,280 --> 00:30:13,290 to the square 947 00:30:13,290 --> 00:30:16,790 to the square is equal to 2a squared and you can find 948 00:30:16,790 --> 00:30:16,800 is equal to 2a squared and you can find 949 00:30:16,800 --> 00:30:20,120 is equal to 2a squared and you can find out that the edge of the unit cell which 950 00:30:20,120 --> 00:30:20,130 out that the edge of the unit cell which 951 00:30:20,130 --> 00:30:25,610 out that the edge of the unit cell which is a will be equal to two times square 952 00:30:25,610 --> 00:30:25,620 is a will be equal to two times square 953 00:30:25,620 --> 00:30:30,100 is a will be equal to two times square root two times the greatest radius of 954 00:30:30,100 --> 00:30:30,110 root two times the greatest radius of 955 00:30:30,110 --> 00:30:33,620 root two times the greatest radius of aluminum radius of the aluminum and if I 956 00:30:33,620 --> 00:30:33,630 aluminum radius of the aluminum and if I 957 00:30:33,630 --> 00:30:36,770 aluminum radius of the aluminum and if I put the values here radius of aluminum 958 00:30:36,770 --> 00:30:36,780 put the values here radius of aluminum 959 00:30:36,780 --> 00:30:41,810 put the values here radius of aluminum as 1.43 and the edge of the unit cell 960 00:30:41,810 --> 00:30:41,820 as 1.43 and the edge of the unit cell 961 00:30:41,820 --> 00:30:47,840 as 1.43 and the edge of the unit cell will turn out to be as 4.0 for let's say 962 00:30:47,840 --> 00:30:47,850 will turn out to be as 4.0 for let's say 963 00:30:47,850 --> 00:30:51,700 will turn out to be as 4.0 for let's say five here angstrom 964 00:30:51,700 --> 00:30:51,710 five here angstrom 965 00:30:51,710 --> 00:30:56,630 five here angstrom clear so that is the edge now if I would 966 00:30:56,630 --> 00:30:56,640 clear so that is the edge now if I would 967 00:30:56,640 --> 00:31:00,200 clear so that is the edge now if I would like to calculate the density in units 968 00:31:00,200 --> 00:31:00,210 like to calculate the density in units 969 00:31:00,210 --> 00:31:04,370 like to calculate the density in units of gram per cubic centimeter it would be 970 00:31:04,370 --> 00:31:04,380 of gram per cubic centimeter it would be 971 00:31:04,380 --> 00:31:07,930 of gram per cubic centimeter it would be wise to convert this actually to the 972 00:31:07,930 --> 00:31:07,940 wise to convert this actually to the 973 00:31:07,940 --> 00:31:11,300 wise to convert this actually to the centimeters right centimeter and if I 974 00:31:11,300 --> 00:31:11,310 centimeters right centimeter and if I 975 00:31:11,310 --> 00:31:13,190 centimeters right centimeter and if I convert it to the centimeter this is 976 00:31:13,190 --> 00:31:13,200 convert it to the centimeter this is 977 00:31:13,200 --> 00:31:17,300 convert it to the centimeter this is going to be simply 4.0 five times ten to 978 00:31:17,300 --> 00:31:17,310 going to be simply 4.0 five times ten to 979 00:31:17,310 --> 00:31:26,860 going to be simply 4.0 five times ten to the what centimeter one angstrom is ten 980 00:31:26,860 --> 00:31:26,870 the what centimeter one angstrom is ten 981 00:31:26,870 --> 00:31:30,620 the what centimeter one angstrom is ten to the eighth right we have to learn 982 00:31:30,620 --> 00:31:30,630 to the eighth right we have to learn 983 00:31:30,630 --> 00:31:32,740 to the eighth right we have to learn these these are very important know 984 00:31:32,740 --> 00:31:32,750 these these are very important know 985 00:31:32,750 --> 00:31:36,110 these these are very important know nanometers angstroms and millimeters and 986 00:31:36,110 --> 00:31:36,120 nanometers angstroms and millimeters and 987 00:31:36,120 --> 00:31:38,960 nanometers angstroms and millimeters and so on but these are simple so it is 10 988 00:31:38,960 --> 00:31:38,970 so on but these are simple so it is 10 989 00:31:38,970 --> 00:31:42,200 so on but these are simple so it is 10 to the minus 8 centimeters 10 to the 990 00:31:42,200 --> 00:31:42,210 to the minus 8 centimeters 10 to the 991 00:31:42,210 --> 00:31:45,020 to the minus 8 centimeters 10 to the minus 8 centimeters now if I simply 992 00:31:45,020 --> 00:31:45,030 minus 8 centimeters now if I simply 993 00:31:45,030 --> 00:31:47,750 minus 8 centimeters now if I simply calculate the volume of the unit cell 994 00:31:47,750 --> 00:31:47,760 calculate the volume of the unit cell 995 00:31:47,760 --> 00:31:51,800 calculate the volume of the unit cell and that will be simply a to the cube 996 00:31:51,800 --> 00:31:51,810 and that will be simply a to the cube 997 00:31:51,810 --> 00:31:56,330 and that will be simply a to the cube and I replace that a here and the volume 998 00:31:56,330 --> 00:31:56,340 and I replace that a here and the volume 999 00:31:56,340 --> 00:31:59,480 and I replace that a here and the volume of the unit cell would be simply equals 1000 00:31:59,480 --> 00:31:59,490 of the unit cell would be simply equals 1001 00:31:59,490 --> 00:32:12,460 of the unit cell would be simply equals to 6 6 2 times 10 to the minus 23 cubic 1002 00:32:12,460 --> 00:32:12,470 to 6 6 2 times 10 to the minus 23 cubic 1003 00:32:12,470 --> 00:32:16,250 to 6 6 2 times 10 to the minus 23 cubic centimeter cubic centimeter now I am 1004 00:32:16,250 --> 00:32:16,260 centimeter cubic centimeter now I am 1005 00:32:16,260 --> 00:32:18,770 centimeter cubic centimeter now I am ready to calculate the density density 1006 00:32:18,770 --> 00:32:18,780 ready to calculate the density density 1007 00:32:18,780 --> 00:32:22,060 ready to calculate the density density of aluminum in fact would be equal to 1008 00:32:22,060 --> 00:32:22,070 of aluminum in fact would be equal to 1009 00:32:22,070 --> 00:32:26,920 of aluminum in fact would be equal to mass of one unit cell which is 1.7 1010 00:32:26,920 --> 00:32:26,930 mass of one unit cell which is 1.7 1011 00:32:26,930 --> 00:32:30,790 mass of one unit cell which is 1.7 9 times 10 to the minus 22 divided by 1012 00:32:30,790 --> 00:32:30,800 9 times 10 to the minus 22 divided by 1013 00:32:30,800 --> 00:32:33,730 9 times 10 to the minus 22 divided by the volume this is graham and that's 1014 00:32:33,730 --> 00:32:33,740 the volume this is graham and that's 1015 00:32:33,740 --> 00:32:38,530 the volume this is graham and that's cubic centimeter six point six two times 1016 00:32:38,530 --> 00:32:38,540 cubic centimeter six point six two times 1017 00:32:38,540 --> 00:32:43,060 cubic centimeter six point six two times ten to the minus 23 cubic centimeter and 1018 00:32:43,060 --> 00:32:43,070 ten to the minus 23 cubic centimeter and 1019 00:32:43,070 --> 00:32:45,550 ten to the minus 23 cubic centimeter and that is equals to if you work it out 1020 00:32:45,550 --> 00:32:45,560 that is equals to if you work it out 1021 00:32:45,560 --> 00:32:48,580 that is equals to if you work it out turns out to be two point seven Oh gram 1022 00:32:48,580 --> 00:32:48,590 turns out to be two point seven Oh gram 1023 00:32:48,590 --> 00:32:53,100 turns out to be two point seven Oh gram per cubic centimeter is the answer for 1024 00:32:53,100 --> 00:32:53,110 per cubic centimeter is the answer for 1025 00:32:53,110 --> 00:32:57,280 per cubic centimeter is the answer for aluminum so you see again by using the 1026 00:32:57,280 --> 00:32:57,290 aluminum so you see again by using the 1027 00:32:57,290 --> 00:33:01,120 aluminum so you see again by using the relationship between the radius of the 1028 00:33:01,120 --> 00:33:01,130 relationship between the radius of the 1029 00:33:01,130 --> 00:33:04,690 relationship between the radius of the atoms and the edges of the unit cell and 1030 00:33:04,690 --> 00:33:04,700 atoms and the edges of the unit cell and 1031 00:33:04,700 --> 00:33:08,050 atoms and the edges of the unit cell and the unit cell we can calculate the 1032 00:33:08,050 --> 00:33:08,060 the unit cell we can calculate the 1033 00:33:08,060 --> 00:33:11,470 the unit cell we can calculate the density if the information here that 1034 00:33:11,470 --> 00:33:11,480 density if the information here that 1035 00:33:11,480 --> 00:33:15,910 density if the information here that like the mass of the atoms and the 1036 00:33:15,910 --> 00:33:15,920 like the mass of the atoms and the 1037 00:33:15,920 --> 00:33:18,280 like the mass of the atoms and the radius of the atoms are given again for 1038 00:33:18,280 --> 00:33:18,290 radius of the atoms are given again for 1039 00:33:18,290 --> 00:33:21,310 radius of the atoms are given again for example I could have given you the 1040 00:33:21,310 --> 00:33:21,320 example I could have given you the 1041 00:33:21,320 --> 00:33:25,540 example I could have given you the density of aluminum and then I would 1042 00:33:25,540 --> 00:33:25,550 density of aluminum and then I would 1043 00:33:25,550 --> 00:33:29,920 density of aluminum and then I would have asked you what is the radius of 1044 00:33:29,920 --> 00:33:29,930 have asked you what is the radius of 1045 00:33:29,930 --> 00:33:33,100 have asked you what is the radius of aluminum assuming that all aluminum 1046 00:33:33,100 --> 00:33:33,110 aluminum assuming that all aluminum 1047 00:33:33,110 --> 00:33:35,920 aluminum assuming that all aluminum atoms are touching each other as in 1048 00:33:35,920 --> 00:33:35,930 atoms are touching each other as in 1049 00:33:35,930 --> 00:33:38,920 atoms are touching each other as in close packed structures or we may ask 1050 00:33:38,920 --> 00:33:38,930 close packed structures or we may ask 1051 00:33:38,930 --> 00:33:41,440 close packed structures or we may ask some other things for example we can 1052 00:33:41,440 --> 00:33:41,450 some other things for example we can 1053 00:33:41,450 --> 00:33:43,300 some other things for example we can give everything here and we can ask you 1054 00:33:43,300 --> 00:33:43,310 give everything here and we can ask you 1055 00:33:43,310 --> 00:33:45,820 give everything here and we can ask you can give you the density we can give you 1056 00:33:45,820 --> 00:33:45,830 can give you the density we can give you 1057 00:33:45,830 --> 00:33:48,910 can give you the density we can give you the radius we can give you the mass of 1058 00:33:48,910 --> 00:33:48,920 the radius we can give you the mass of 1059 00:33:48,920 --> 00:33:53,980 the radius we can give you the mass of the aluminum actually atomic mass there 1060 00:33:53,980 --> 00:33:53,990 the aluminum actually atomic mass there 1061 00:33:53,990 --> 00:33:57,010 the aluminum actually atomic mass there and we can ask you to calculate the 1062 00:33:57,010 --> 00:33:57,020 and we can ask you to calculate the 1063 00:33:57,020 --> 00:34:01,420 and we can ask you to calculate the Avogadro's number right you can do that 1064 00:34:01,420 --> 00:34:01,430 Avogadro's number right you can do that 1065 00:34:01,430 --> 00:34:04,870 Avogadro's number right you can do that because in this calculation you know if 1066 00:34:04,870 --> 00:34:04,880 because in this calculation you know if 1067 00:34:04,880 --> 00:34:06,280 because in this calculation you know if you don't know how a god Rose number and 1068 00:34:06,280 --> 00:34:06,290 you don't know how a god Rose number and 1069 00:34:06,290 --> 00:34:08,170 you don't know how a god Rose number and if you know all the others you can 1070 00:34:08,170 --> 00:34:08,180 if you know all the others you can 1071 00:34:08,180 --> 00:34:10,720 if you know all the others you can calculate it actually the Avogadro's 1072 00:34:10,720 --> 00:34:10,730 calculate it actually the Avogadro's 1073 00:34:10,730 --> 00:34:12,670 calculate it actually the Avogadro's number calculated from these crystalline 1074 00:34:12,670 --> 00:34:12,680 number calculated from these crystalline 1075 00:34:12,680 --> 00:34:15,070 number calculated from these crystalline solids turns out to be very very close 1076 00:34:15,070 --> 00:34:15,080 solids turns out to be very very close 1077 00:34:15,080 --> 00:34:19,120 solids turns out to be very very close to 6.0 to 10 to the 23 that's very 1078 00:34:19,120 --> 00:34:19,130 to 6.0 to 10 to the 23 that's very 1079 00:34:19,130 --> 00:34:21,730 to 6.0 to 10 to the 23 that's very important very important as a matter of 1080 00:34:21,730 --> 00:34:21,740 important very important as a matter of 1081 00:34:21,740 --> 00:34:24,940 important very important as a matter of fact and that that's one way of you know 1082 00:34:24,940 --> 00:34:24,950 fact and that that's one way of you know 1083 00:34:24,950 --> 00:34:27,460 fact and that that's one way of you know experimentally shown that the Avogadro's 1084 00:34:27,460 --> 00:34:27,470 experimentally shown that the Avogadro's 1085 00:34:27,470 --> 00:34:31,150 experimentally shown that the Avogadro's number is right a correct number yes 1086 00:34:31,150 --> 00:34:31,160 number is right a correct number yes 1087 00:34:31,160 --> 00:34:38,579 number is right a correct number yes any questions 1088 00:34:38,579 --> 00:34:38,589 1089 00:34:38,589 --> 00:34:41,589 how close we how close we get it 1090 00:34:41,589 --> 00:34:41,599 how close we how close we get it 1091 00:34:41,599 --> 00:34:44,200 how close we how close we get it actually it says estimate the it is 1092 00:34:44,200 --> 00:34:44,210 actually it says estimate the it is 1093 00:34:44,210 --> 00:34:48,250 actually it says estimate the it is pretty close I mean the value of the 1094 00:34:48,250 --> 00:34:48,260 pretty close I mean the value of the 1095 00:34:48,260 --> 00:34:50,260 pretty close I mean the value of the aluminum I can't remember exactly but 1096 00:34:50,260 --> 00:34:50,270 aluminum I can't remember exactly but 1097 00:34:50,270 --> 00:34:54,760 aluminum I can't remember exactly but it's somewhere about 2.7 3 maybe 75 and 1098 00:34:54,760 --> 00:34:54,770 it's somewhere about 2.7 3 maybe 75 and 1099 00:34:54,770 --> 00:35:10,539 it's somewhere about 2.7 3 maybe 75 and so on yes no no I don't I don't have to 1100 00:35:10,539 --> 00:35:10,549 so on yes no no I don't I don't have to 1101 00:35:10,549 --> 00:35:13,620 so on yes no no I don't I don't have to consider the empty spaces in this case 1102 00:35:13,620 --> 00:35:13,630 consider the empty spaces in this case 1103 00:35:13,630 --> 00:35:18,819 consider the empty spaces in this case right you can you can probably set up 1104 00:35:18,819 --> 00:35:18,829 right you can you can probably set up 1105 00:35:18,829 --> 00:35:20,829 right you can you can probably set up your problem such that since this is a 1106 00:35:20,829 --> 00:35:20,839 your problem such that since this is a 1107 00:35:20,839 --> 00:35:23,079 your problem such that since this is a closed pack structure the packing 1108 00:35:23,079 --> 00:35:23,089 closed pack structure the packing 1109 00:35:23,089 --> 00:35:27,779 closed pack structure the packing efficiency is 76% what percent is empty 1110 00:35:27,779 --> 00:35:27,789 efficiency is 76% what percent is empty 1111 00:35:27,789 --> 00:35:33,609 efficiency is 76% what percent is empty and no no no because in that case you 1112 00:35:33,609 --> 00:35:33,619 and no no no because in that case you 1113 00:35:33,619 --> 00:35:39,250 and no no no because in that case you have to know the density of one aluminum 1114 00:35:39,250 --> 00:35:39,260 have to know the density of one aluminum 1115 00:35:39,260 --> 00:35:42,549 have to know the density of one aluminum atomosphere which is not possible 1116 00:35:42,549 --> 00:35:42,559 atomosphere which is not possible 1117 00:35:42,559 --> 00:35:45,579 atomosphere which is not possible actually right that would be very very 1118 00:35:45,579 --> 00:35:45,589 actually right that would be very very 1119 00:35:45,589 --> 00:35:52,299 actually right that would be very very heavy yes how I found the coordination 1120 00:35:52,299 --> 00:35:52,309 heavy yes how I found the coordination 1121 00:35:52,309 --> 00:35:53,140 heavy yes how I found the coordination number okay 1122 00:35:53,140 --> 00:35:53,150 number okay 1123 00:35:53,150 --> 00:35:58,329 number okay if you have a close-packed lettuce now 1124 00:35:58,329 --> 00:35:58,339 if you have a close-packed lettuce now 1125 00:35:58,339 --> 00:36:00,910 if you have a close-packed lettuce now school clothes packed letters made off 1126 00:36:00,910 --> 00:36:00,920 school clothes packed letters made off 1127 00:36:00,920 --> 00:36:04,380 school clothes packed letters made off from the same size atoms same size atoms 1128 00:36:04,380 --> 00:36:04,390 from the same size atoms same size atoms 1129 00:36:04,390 --> 00:36:08,859 from the same size atoms same size atoms coordination number is always 12 where 1130 00:36:08,859 --> 00:36:08,869 coordination number is always 12 where 1131 00:36:08,869 --> 00:36:10,630 coordination number is always 12 where do I know it's a closed pack because the 1132 00:36:10,630 --> 00:36:10,640 do I know it's a closed pack because the 1133 00:36:10,640 --> 00:36:15,609 do I know it's a closed pack because the unit cell is face centered cubic and 1134 00:36:15,609 --> 00:36:15,619 unit cell is face centered cubic and 1135 00:36:15,619 --> 00:36:19,120 unit cell is face centered cubic and only the close packed structures will 1136 00:36:19,120 --> 00:36:19,130 only the close packed structures will 1137 00:36:19,130 --> 00:36:22,089 only the close packed structures will have the phase centered cubic unit cell 1138 00:36:22,089 --> 00:36:22,099 have the phase centered cubic unit cell 1139 00:36:22,099 --> 00:36:24,670 have the phase centered cubic unit cell again assuming that all atoms are 1140 00:36:24,670 --> 00:36:24,680 again assuming that all atoms are 1141 00:36:24,680 --> 00:36:32,110 again assuming that all atoms are touching each other 1142 00:36:32,110 --> 00:36:32,120 1143 00:36:32,120 --> 00:36:35,420 okay now the next we will talk about 1144 00:36:35,420 --> 00:36:35,430 okay now the next we will talk about 1145 00:36:35,430 --> 00:36:49,740 okay now the next we will talk about ellos 1146 00:36:49,740 --> 00:36:49,750 1147 00:36:49,750 --> 00:36:56,630 and alloys are also very important 1148 00:36:56,630 --> 00:36:56,640 and alloys are also very important 1149 00:36:56,640 --> 00:37:01,470 and alloys are also very important remember alloys are the mixtures of the 1150 00:37:01,470 --> 00:37:01,480 remember alloys are the mixtures of the 1151 00:37:01,480 --> 00:37:05,600 remember alloys are the mixtures of the elements which have metallic properties 1152 00:37:05,600 --> 00:37:05,610 elements which have metallic properties 1153 00:37:05,610 --> 00:37:09,360 elements which have metallic properties so all alloys should have a metallic 1154 00:37:09,360 --> 00:37:09,370 so all alloys should have a metallic 1155 00:37:09,370 --> 00:37:12,480 so all alloys should have a metallic properties actually another way of 1156 00:37:12,480 --> 00:37:12,490 properties actually another way of 1157 00:37:12,490 --> 00:37:17,400 properties actually another way of defining alloys is called the solid 1158 00:37:17,400 --> 00:37:17,410 defining alloys is called the solid 1159 00:37:17,410 --> 00:37:20,640 defining alloys is called the solid solutions of metal solid solutions of 1160 00:37:20,640 --> 00:37:20,650 solutions of metal solid solutions of 1161 00:37:20,650 --> 00:37:24,030 solutions of metal solid solutions of metals are simply alloys or that that 1162 00:37:24,030 --> 00:37:24,040 metals are simply alloys or that that 1163 00:37:24,040 --> 00:37:28,220 metals are simply alloys or that that means that the alloys are homogeneous 1164 00:37:28,220 --> 00:37:28,230 means that the alloys are homogeneous 1165 00:37:28,230 --> 00:37:31,230 means that the alloys are homogeneous mixtures of the elements right 1166 00:37:31,230 --> 00:37:31,240 mixtures of the elements right 1167 00:37:31,240 --> 00:37:34,380 mixtures of the elements right homogeneous mixtures of the elements now 1168 00:37:34,380 --> 00:37:34,390 homogeneous mixtures of the elements now 1169 00:37:34,390 --> 00:37:40,260 homogeneous mixtures of the elements now by simply alloying and metal in fact you 1170 00:37:40,260 --> 00:37:40,270 by simply alloying and metal in fact you 1171 00:37:40,270 --> 00:37:42,810 by simply alloying and metal in fact you can change the properties of that metal 1172 00:37:42,810 --> 00:37:42,820 can change the properties of that metal 1173 00:37:42,820 --> 00:37:45,300 can change the properties of that metal you can increase the strength you can 1174 00:37:45,300 --> 00:37:45,310 you can increase the strength you can 1175 00:37:45,310 --> 00:37:47,880 you can increase the strength you can increase the resistance to corrosion and 1176 00:37:47,880 --> 00:37:47,890 increase the resistance to corrosion and 1177 00:37:47,890 --> 00:37:51,180 increase the resistance to corrosion and you can increase the boiling point and 1178 00:37:51,180 --> 00:37:51,190 you can increase the boiling point and 1179 00:37:51,190 --> 00:37:54,690 you can increase the boiling point and so on so therefore by simply preparing 1180 00:37:54,690 --> 00:37:54,700 so on so therefore by simply preparing 1181 00:37:54,700 --> 00:37:58,740 so on so therefore by simply preparing alloys mixing the elements to form 1182 00:37:58,740 --> 00:37:58,750 alloys mixing the elements to form 1183 00:37:58,750 --> 00:38:04,440 alloys mixing the elements to form alloys you may simply obtain the solid 1184 00:38:04,440 --> 00:38:04,450 alloys you may simply obtain the solid 1185 00:38:04,450 --> 00:38:08,430 alloys you may simply obtain the solid which have particular properties that 1186 00:38:08,430 --> 00:38:08,440 which have particular properties that 1187 00:38:08,440 --> 00:38:11,100 which have particular properties that you want and that's possible now the 1188 00:38:11,100 --> 00:38:11,110 you want and that's possible now the 1189 00:38:11,110 --> 00:38:15,060 you want and that's possible now the alloys are are also classified here or 1190 00:38:15,060 --> 00:38:15,070 alloys are are also classified here or 1191 00:38:15,070 --> 00:38:17,130 alloys are are also classified here or this simply gives the some of the 1192 00:38:17,130 --> 00:38:17,140 this simply gives the some of the 1193 00:38:17,140 --> 00:38:20,880 this simply gives the some of the examples of the alloys if you go through 1194 00:38:20,880 --> 00:38:20,890 examples of the alloys if you go through 1195 00:38:20,890 --> 00:38:24,930 examples of the alloys if you go through here as you see again we have for 1196 00:38:24,930 --> 00:38:24,940 here as you see again we have for 1197 00:38:24,940 --> 00:38:28,470 here as you see again we have for example bronze and we have brass and 1198 00:38:28,470 --> 00:38:28,480 example bronze and we have brass and 1199 00:38:28,480 --> 00:38:31,020 example bronze and we have brass and those are the copper and zinc and copper 1200 00:38:31,020 --> 00:38:31,030 those are the copper and zinc and copper 1201 00:38:31,030 --> 00:38:34,670 those are the copper and zinc and copper and tin but the most known alloys that 1202 00:38:34,670 --> 00:38:34,680 and tin but the most known alloys that 1203 00:38:34,680 --> 00:38:37,520 and tin but the most known alloys that we come across everyday and use it are 1204 00:38:37,520 --> 00:38:37,530 we come across everyday and use it are 1205 00:38:37,530 --> 00:38:41,310 we come across everyday and use it are stainless steel right stainless steels 1206 00:38:41,310 --> 00:38:41,320 stainless steel right stainless steels 1207 00:38:41,320 --> 00:38:45,980 stainless steel right stainless steels are alloys of iron and carbon and 1208 00:38:45,980 --> 00:38:45,990 are alloys of iron and carbon and 1209 00:38:45,990 --> 00:38:49,500 are alloys of iron and carbon and chromium and depending on again nickel 1210 00:38:49,500 --> 00:38:49,510 chromium and depending on again nickel 1211 00:38:49,510 --> 00:38:53,340 chromium and depending on again nickel you may have nickel there too but almost 1212 00:38:53,340 --> 00:38:53,350 you may have nickel there too but almost 1213 00:38:53,350 --> 00:38:56,970 you may have nickel there too but almost all items that is used in industry are 1214 00:38:56,970 --> 00:38:56,980 all items that is used in industry are 1215 00:38:56,980 --> 00:39:00,300 all items that is used in industry are alloys of iron this way you increase the 1216 00:39:00,300 --> 00:39:00,310 alloys of iron this way you increase the 1217 00:39:00,310 --> 00:39:01,910 alloys of iron this way you increase the strength of iron 1218 00:39:01,910 --> 00:39:01,920 strength of iron 1219 00:39:01,920 --> 00:39:04,339 strength of iron you increase the corrosion resistance to 1220 00:39:04,339 --> 00:39:04,349 you increase the corrosion resistance to 1221 00:39:04,349 --> 00:39:06,859 you increase the corrosion resistance to the corrosion stainless steel actually 1222 00:39:06,859 --> 00:39:06,869 the corrosion stainless steel actually 1223 00:39:06,869 --> 00:39:10,630 the corrosion stainless steel actually it's simply that says that is very 1224 00:39:10,630 --> 00:39:10,640 it's simply that says that is very 1225 00:39:10,640 --> 00:39:13,099 it's simply that says that is very corrosion resistant substance corrosion 1226 00:39:13,099 --> 00:39:13,109 corrosion resistant substance corrosion 1227 00:39:13,109 --> 00:39:15,740 corrosion resistant substance corrosion resistant substance again sometimes we 1228 00:39:15,740 --> 00:39:15,750 resistant substance again sometimes we 1229 00:39:15,750 --> 00:39:19,789 resistant substance again sometimes we want a very strong substance but low 1230 00:39:19,789 --> 00:39:19,799 want a very strong substance but low 1231 00:39:19,799 --> 00:39:23,000 want a very strong substance but low density and sometimes we want substance 1232 00:39:23,000 --> 00:39:23,010 density and sometimes we want substance 1233 00:39:23,010 --> 00:39:26,720 density and sometimes we want substance that will have very high melting points 1234 00:39:26,720 --> 00:39:26,730 that will have very high melting points 1235 00:39:26,730 --> 00:39:29,599 that will have very high melting points and so on so all of these are done by 1236 00:39:29,599 --> 00:39:29,609 and so on so all of these are done by 1237 00:39:29,609 --> 00:39:34,099 and so on so all of these are done by alloying simply the elements types of 1238 00:39:34,099 --> 00:39:34,109 alloying simply the elements types of 1239 00:39:34,109 --> 00:39:36,620 alloying simply the elements types of alloys we classify the alloys one is 1240 00:39:36,620 --> 00:39:36,630 alloys we classify the alloys one is 1241 00:39:36,630 --> 00:39:39,710 alloys we classify the alloys one is called the substitutional alloys and the 1242 00:39:39,710 --> 00:39:39,720 called the substitutional alloys and the 1243 00:39:39,720 --> 00:39:41,780 called the substitutional alloys and the other one is called interstitial alloys 1244 00:39:41,780 --> 00:39:41,790 other one is called interstitial alloys 1245 00:39:41,790 --> 00:39:45,910 other one is called interstitial alloys and then we have heterogeneous alloys 1246 00:39:45,910 --> 00:39:45,920 and then we have heterogeneous alloys 1247 00:39:45,920 --> 00:39:50,200 and then we have heterogeneous alloys now in addition to that we also have 1248 00:39:50,200 --> 00:39:50,210 now in addition to that we also have 1249 00:39:50,210 --> 00:39:56,059 now in addition to that we also have compounds alloys which are the compounds 1250 00:39:56,059 --> 00:39:56,069 compounds alloys which are the compounds 1251 00:39:56,069 --> 00:39:57,620 compounds alloys which are the compounds of metal actually these are metal 1252 00:39:57,620 --> 00:39:57,630 of metal actually these are metal 1253 00:39:57,630 --> 00:40:01,640 of metal actually these are metal compounds and they have very distinct 1254 00:40:01,640 --> 00:40:01,650 compounds and they have very distinct 1255 00:40:01,650 --> 00:40:04,250 compounds and they have very distinct properties as we will talk about that 1256 00:40:04,250 --> 00:40:04,260 properties as we will talk about that 1257 00:40:04,260 --> 00:40:07,940 properties as we will talk about that but let's look at again those three 1258 00:40:07,940 --> 00:40:07,950 but let's look at again those three 1259 00:40:07,950 --> 00:40:10,670 but let's look at again those three types of alloys here substitutional 1260 00:40:10,670 --> 00:40:10,680 types of alloys here substitutional 1261 00:40:10,680 --> 00:40:13,849 types of alloys here substitutional alloys it says a second element takes 1262 00:40:13,849 --> 00:40:13,859 alloys it says a second element takes 1263 00:40:13,859 --> 00:40:17,089 alloys it says a second element takes the place of a metal atom that means you 1264 00:40:17,089 --> 00:40:17,099 the place of a metal atom that means you 1265 00:40:17,099 --> 00:40:23,559 the place of a metal atom that means you simply mix the two element together and 1266 00:40:23,559 --> 00:40:23,569 simply mix the two element together and 1267 00:40:23,569 --> 00:40:28,210 simply mix the two element together and you consider that the second element is 1268 00:40:28,210 --> 00:40:28,220 you consider that the second element is 1269 00:40:28,220 --> 00:40:31,670 you consider that the second element is replaces some of the atoms of the first 1270 00:40:31,670 --> 00:40:31,680 replaces some of the atoms of the first 1271 00:40:31,680 --> 00:40:35,359 replaces some of the atoms of the first element in the lattice right in the 1272 00:40:35,359 --> 00:40:35,369 element in the lattice right in the 1273 00:40:35,369 --> 00:40:38,420 element in the lattice right in the lattice for example as we have here 1274 00:40:38,420 --> 00:40:38,430 lattice for example as we have here 1275 00:40:38,430 --> 00:40:41,930 lattice for example as we have here usually the silver and gold alloys are 1276 00:40:41,930 --> 00:40:41,940 usually the silver and gold alloys are 1277 00:40:41,940 --> 00:40:43,130 usually the silver and gold alloys are like that 1278 00:40:43,130 --> 00:40:43,140 like that 1279 00:40:43,140 --> 00:40:46,900 like that then you mix silver and gold silver 1280 00:40:46,900 --> 00:40:46,910 then you mix silver and gold silver 1281 00:40:46,910 --> 00:40:49,760 then you mix silver and gold silver replaces some of the alloys in the 1282 00:40:49,760 --> 00:40:49,770 replaces some of the alloys in the 1283 00:40:49,770 --> 00:40:52,430 replaces some of the alloys in the lattice points for example it is forming 1284 00:40:52,430 --> 00:40:52,440 lattice points for example it is forming 1285 00:40:52,440 --> 00:40:54,770 lattice points for example it is forming if it is forming a cubic face-centered 1286 00:40:54,770 --> 00:40:54,780 if it is forming a cubic face-centered 1287 00:40:54,780 --> 00:40:58,130 if it is forming a cubic face-centered cubic lattice gold and the silver goes 1288 00:40:58,130 --> 00:40:58,140 cubic lattice gold and the silver goes 1289 00:40:58,140 --> 00:41:02,690 cubic lattice gold and the silver goes and replaces one of the gold atom in 1290 00:41:02,690 --> 00:41:02,700 and replaces one of the gold atom in 1291 00:41:02,700 --> 00:41:05,059 and replaces one of the gold atom in fact in that structure in that letters 1292 00:41:05,059 --> 00:41:05,069 fact in that structure in that letters 1293 00:41:05,069 --> 00:41:07,900 fact in that structure in that letters and those kind of alloys are called 1294 00:41:07,900 --> 00:41:07,910 and those kind of alloys are called 1295 00:41:07,910 --> 00:41:10,750 and those kind of alloys are called substitutional alloys as you say you 1296 00:41:10,750 --> 00:41:10,760 substitutional alloys as you say you 1297 00:41:10,760 --> 00:41:15,540 substitutional alloys as you say you substitute gold by silver 1298 00:41:15,540 --> 00:41:15,550 substitute gold by silver 1299 00:41:15,550 --> 00:41:19,200 substitute gold by silver example in gold and silver alloys now 1300 00:41:19,200 --> 00:41:19,210 example in gold and silver alloys now 1301 00:41:19,210 --> 00:41:23,700 example in gold and silver alloys now for this we should have the size of the 1302 00:41:23,700 --> 00:41:23,710 for this we should have the size of the 1303 00:41:23,710 --> 00:41:28,020 for this we should have the size of the metal atoms close to each other if the 1304 00:41:28,020 --> 00:41:28,030 metal atoms close to each other if the 1305 00:41:28,030 --> 00:41:30,540 metal atoms close to each other if the sizes are very different then we can't 1306 00:41:30,540 --> 00:41:30,550 sizes are very different then we can't 1307 00:41:30,550 --> 00:41:33,620 sizes are very different then we can't really do that right the size has to be 1308 00:41:33,620 --> 00:41:33,630 really do that right the size has to be 1309 00:41:33,630 --> 00:41:37,200 really do that right the size has to be about the same so that one atom will 1310 00:41:37,200 --> 00:41:37,210 about the same so that one atom will 1311 00:41:37,210 --> 00:41:39,810 about the same so that one atom will replace the other atom in the lattice 1312 00:41:39,810 --> 00:41:39,820 replace the other atom in the lattice 1313 00:41:39,820 --> 00:41:42,630 replace the other atom in the lattice without disturbing the lattice structure 1314 00:41:42,630 --> 00:41:42,640 without disturbing the lattice structure 1315 00:41:42,640 --> 00:41:44,490 without disturbing the lattice structure without disturbing the lattice structure 1316 00:41:44,490 --> 00:41:44,500 without disturbing the lattice structure 1317 00:41:44,500 --> 00:41:51,570 without disturbing the lattice structure actually gold pure gold is very soft to 1318 00:41:51,570 --> 00:41:51,580 actually gold pure gold is very soft to 1319 00:41:51,580 --> 00:41:54,330 actually gold pure gold is very soft to make jewelry and so on most of the gold 1320 00:41:54,330 --> 00:41:54,340 make jewelry and so on most of the gold 1321 00:41:54,340 --> 00:41:58,010 make jewelry and so on most of the gold jewelry's are alloys of gold with silver 1322 00:41:58,010 --> 00:41:58,020 jewelry's are alloys of gold with silver 1323 00:41:58,020 --> 00:42:01,520 jewelry's are alloys of gold with silver with copper with certain percent again 1324 00:42:01,520 --> 00:42:01,530 with copper with certain percent again 1325 00:42:01,530 --> 00:42:05,730 with copper with certain percent again that's what we simply have when we buy 1326 00:42:05,730 --> 00:42:05,740 that's what we simply have when we buy 1327 00:42:05,740 --> 00:42:08,100 that's what we simply have when we buy gold jewelry's actually not they're not 1328 00:42:08,100 --> 00:42:08,110 gold jewelry's actually not they're not 1329 00:42:08,110 --> 00:42:12,000 gold jewelry's actually not they're not pure gold now interstitial alloys in 1330 00:42:12,000 --> 00:42:12,010 pure gold now interstitial alloys in 1331 00:42:12,010 --> 00:42:17,360 pure gold now interstitial alloys in this case the second element atom do not 1332 00:42:17,360 --> 00:42:17,370 this case the second element atom do not 1333 00:42:17,370 --> 00:42:20,640 this case the second element atom do not replaces in the crystal letters of the 1334 00:42:20,640 --> 00:42:20,650 replaces in the crystal letters of the 1335 00:42:20,650 --> 00:42:23,790 replaces in the crystal letters of the first element atom but it goes between 1336 00:42:23,790 --> 00:42:23,800 first element atom but it goes between 1337 00:42:23,800 --> 00:42:26,820 first element atom but it goes between the layers between the empty spaces like 1338 00:42:26,820 --> 00:42:26,830 the layers between the empty spaces like 1339 00:42:26,830 --> 00:42:29,130 the layers between the empty spaces like it may go to tetrahedral or octahedral 1340 00:42:29,130 --> 00:42:29,140 it may go to tetrahedral or octahedral 1341 00:42:29,140 --> 00:42:33,810 it may go to tetrahedral or octahedral holes right and that kind of alloys are 1342 00:42:33,810 --> 00:42:33,820 holes right and that kind of alloys are 1343 00:42:33,820 --> 00:42:34,230 holes right and that kind of alloys are called 1344 00:42:34,230 --> 00:42:34,240 called 1345 00:42:34,240 --> 00:42:38,310 called interstitial alloys for example if an 1346 00:42:38,310 --> 00:42:38,320 interstitial alloys for example if an 1347 00:42:38,320 --> 00:42:41,090 interstitial alloys for example if an atom second atom goes into the 1348 00:42:41,090 --> 00:42:41,100 atom second atom goes into the 1349 00:42:41,100 --> 00:42:44,280 atom second atom goes into the octahedral holes then it will simply 1350 00:42:44,280 --> 00:42:44,290 octahedral holes then it will simply 1351 00:42:44,290 --> 00:42:48,090 octahedral holes then it will simply coordinate to six other atoms and 1352 00:42:48,090 --> 00:42:48,100 coordinate to six other atoms and 1353 00:42:48,100 --> 00:42:50,520 coordinate to six other atoms and increase the bond strength and this way 1354 00:42:50,520 --> 00:42:50,530 increase the bond strength and this way 1355 00:42:50,530 --> 00:42:53,210 increase the bond strength and this way actually you increase the bond strength 1356 00:42:53,210 --> 00:42:53,220 actually you increase the bond strength 1357 00:42:53,220 --> 00:42:58,140 actually you increase the bond strength of the solids and what does that mean is 1358 00:42:58,140 --> 00:42:58,150 of the solids and what does that mean is 1359 00:42:58,150 --> 00:43:01,050 of the solids and what does that mean is that increases the melting point 1360 00:43:01,050 --> 00:43:01,060 that increases the melting point 1361 00:43:01,060 --> 00:43:05,100 that increases the melting point increases the hardness of the metal 1362 00:43:05,100 --> 00:43:05,110 increases the hardness of the metal 1363 00:43:05,110 --> 00:43:07,980 increases the hardness of the metal actually the initial metal now the third 1364 00:43:07,980 --> 00:43:07,990 actually the initial metal now the third 1365 00:43:07,990 --> 00:43:10,710 actually the initial metal now the third is called a heterogeneous alloy this is 1366 00:43:10,710 --> 00:43:10,720 is called a heterogeneous alloy this is 1367 00:43:10,720 --> 00:43:12,900 is called a heterogeneous alloy this is the count components not dispersed 1368 00:43:12,900 --> 00:43:12,910 the count components not dispersed 1369 00:43:12,910 --> 00:43:16,440 the count components not dispersed uniformly actually if we assume that the 1370 00:43:16,440 --> 00:43:16,450 uniformly actually if we assume that the 1371 00:43:16,450 --> 00:43:20,360 uniformly actually if we assume that the if you define a loyal as solids 1372 00:43:20,360 --> 00:43:20,370 if you define a loyal as solids 1373 00:43:20,370 --> 00:43:24,270 if you define a loyal as solids solutions of metals and this is not 1374 00:43:24,270 --> 00:43:24,280 solutions of metals and this is not 1375 00:43:24,280 --> 00:43:26,550 solutions of metals and this is not there right because at your juniors 1376 00:43:26,550 --> 00:43:26,560 there right because at your juniors 1377 00:43:26,560 --> 00:43:28,950 there right because at your juniors solutions is always homogeneous 1378 00:43:28,950 --> 00:43:28,960 solutions is always homogeneous 1379 00:43:28,960 --> 00:43:32,010 solutions is always homogeneous you can't have a genius solutions but 1380 00:43:32,010 --> 00:43:32,020 you can't have a genius solutions but 1381 00:43:32,020 --> 00:43:34,710 you can't have a genius solutions but there are arrows where you have for 1382 00:43:34,710 --> 00:43:34,720 there are arrows where you have for 1383 00:43:34,720 --> 00:43:38,390 there are arrows where you have for example like this one this is again 1384 00:43:38,390 --> 00:43:38,400 example like this one this is again 1385 00:43:38,400 --> 00:43:44,190 example like this one this is again steel iron and carbon alloy and you have 1386 00:43:44,190 --> 00:43:44,200 steel iron and carbon alloy and you have 1387 00:43:44,200 --> 00:43:50,430 steel iron and carbon alloy and you have here this carbon and iron and here we 1388 00:43:50,430 --> 00:43:50,440 here this carbon and iron and here we 1389 00:43:50,440 --> 00:43:52,770 here this carbon and iron and here we have pure iron so that's the sort of a 1390 00:43:52,770 --> 00:43:52,780 have pure iron so that's the sort of a 1391 00:43:52,780 --> 00:43:56,660 have pure iron so that's the sort of a homogeneous heterogeneous type alloys 1392 00:43:56,660 --> 00:43:56,670 homogeneous heterogeneous type alloys 1393 00:43:56,670 --> 00:44:00,150 homogeneous heterogeneous type alloys now inter metallic compounds these are 1394 00:44:00,150 --> 00:44:00,160 now inter metallic compounds these are 1395 00:44:00,160 --> 00:44:02,400 now inter metallic compounds these are simply compounds that simply means that 1396 00:44:02,400 --> 00:44:02,410 simply compounds that simply means that 1397 00:44:02,410 --> 00:44:07,080 simply compounds that simply means that you can only have constant fixed ratio 1398 00:44:07,080 --> 00:44:07,090 you can only have constant fixed ratio 1399 00:44:07,090 --> 00:44:10,140 you can only have constant fixed ratio of the atoms because to have a compound 1400 00:44:10,140 --> 00:44:10,150 of the atoms because to have a compound 1401 00:44:10,150 --> 00:44:13,560 of the atoms because to have a compound remember the ratio of the elements 1402 00:44:13,560 --> 00:44:13,570 remember the ratio of the elements 1403 00:44:13,570 --> 00:44:15,450 remember the ratio of the elements should be the same it shouldn't change 1404 00:44:15,450 --> 00:44:15,460 should be the same it shouldn't change 1405 00:44:15,460 --> 00:44:18,960 should be the same it shouldn't change in other alloys you can increase or 1406 00:44:18,960 --> 00:44:18,970 in other alloys you can increase or 1407 00:44:18,970 --> 00:44:21,690 in other alloys you can increase or decrease the percentages of one element 1408 00:44:21,690 --> 00:44:21,700 decrease the percentages of one element 1409 00:44:21,700 --> 00:44:24,390 decrease the percentages of one element on still it is the alloy even though the 1410 00:44:24,390 --> 00:44:24,400 on still it is the alloy even though the 1411 00:44:24,400 --> 00:44:26,070 on still it is the alloy even though the properties will change a little bit but 1412 00:44:26,070 --> 00:44:26,080 properties will change a little bit but 1413 00:44:26,080 --> 00:44:27,860 properties will change a little bit but it will be the alloy but in this case 1414 00:44:27,860 --> 00:44:27,870 it will be the alloy but in this case 1415 00:44:27,870 --> 00:44:31,260 it will be the alloy but in this case for the inter metallic compounds the 1416 00:44:31,260 --> 00:44:31,270 for the inter metallic compounds the 1417 00:44:31,270 --> 00:44:34,800 for the inter metallic compounds the ratio will never change for example this 1418 00:44:34,800 --> 00:44:34,810 ratio will never change for example this 1419 00:44:34,810 --> 00:44:37,320 ratio will never change for example this one over here three nickel and one 1420 00:44:37,320 --> 00:44:37,330 one over here three nickel and one 1421 00:44:37,330 --> 00:44:40,620 one over here three nickel and one aluminum and this is the structure of 1422 00:44:40,620 --> 00:44:40,630 aluminum and this is the structure of 1423 00:44:40,630 --> 00:44:43,980 aluminum and this is the structure of this compound in the solid state you see 1424 00:44:43,980 --> 00:44:43,990 this compound in the solid state you see 1425 00:44:43,990 --> 00:44:46,620 this compound in the solid state you see how the aluminum and the nickels in fact 1426 00:44:46,620 --> 00:44:46,630 how the aluminum and the nickels in fact 1427 00:44:46,630 --> 00:44:49,910 how the aluminum and the nickels in fact are stacked together this is like a 1428 00:44:49,910 --> 00:44:49,920 are stacked together this is like a 1429 00:44:49,920 --> 00:44:52,830 are stacked together this is like a compound you know just compound and then 1430 00:44:52,830 --> 00:44:52,840 compound you know just compound and then 1431 00:44:52,840 --> 00:44:55,110 compound you know just compound and then you have this one here and then you have 1432 00:44:55,110 --> 00:44:55,120 you have this one here and then you have 1433 00:44:55,120 --> 00:44:57,810 you have this one here and then you have that one here now what is it using these 1434 00:44:57,810 --> 00:44:57,820 that one here now what is it using these 1435 00:44:57,820 --> 00:45:00,480 that one here now what is it using these have very very different properties for 1436 00:45:00,480 --> 00:45:00,490 have very very different properties for 1437 00:45:00,490 --> 00:45:02,880 have very very different properties for example this one is used to make 1438 00:45:02,880 --> 00:45:02,890 example this one is used to make 1439 00:45:02,890 --> 00:45:07,790 example this one is used to make permanent magnets permanent magnet for 1440 00:45:07,790 --> 00:45:07,800 permanent magnets permanent magnet for 1441 00:45:07,800 --> 00:45:11,360 permanent magnets permanent magnet for magnetic circular magnetic resonance 1442 00:45:11,360 --> 00:45:11,370 magnetic circular magnetic resonance 1443 00:45:11,370 --> 00:45:16,290 magnetic circular magnetic resonance instruments or EMR instruments mr images 1444 00:45:16,290 --> 00:45:16,300 instruments or EMR instruments mr images 1445 00:45:16,300 --> 00:45:18,030 instruments or EMR instruments mr images remember those instruments 1446 00:45:18,030 --> 00:45:18,040 remember those instruments 1447 00:45:18,040 --> 00:45:23,670 remember those instruments now this one is superconductor below 19 1448 00:45:23,670 --> 00:45:23,680 now this one is superconductor below 19 1449 00:45:23,680 --> 00:45:26,340 now this one is superconductor below 19 degrees centigrade and it's also used as 1450 00:45:26,340 --> 00:45:26,350 degrees centigrade and it's also used as 1451 00:45:26,350 --> 00:45:29,040 degrees centigrade and it's also used as a superconductor in fact and you know 1452 00:45:29,040 --> 00:45:29,050 a superconductor in fact and you know 1453 00:45:29,050 --> 00:45:31,500 a superconductor in fact and you know they have very different properties as a 1454 00:45:31,500 --> 00:45:31,510 they have very different properties as a 1455 00:45:31,510 --> 00:45:34,250 they have very different properties as a matter of fact and again you see 1456 00:45:34,250 --> 00:45:34,260 matter of fact and again you see 1457 00:45:34,260 --> 00:45:36,930 matter of fact and again you see distinct properties definite composition 1458 00:45:36,930 --> 00:45:36,940 distinct properties definite composition 1459 00:45:36,940 --> 00:45:40,110 distinct properties definite composition this is important to be a compound you 1460 00:45:40,110 --> 00:45:40,120 this is important to be a compound you 1461 00:45:40,120 --> 00:45:42,329 this is important to be a compound you have to have a definite composite 1462 00:45:42,329 --> 00:45:42,339 have to have a definite composite 1463 00:45:42,339 --> 00:45:44,790 have to have a definite composite ordered rather than randomly distributed 1464 00:45:44,790 --> 00:45:44,800 ordered rather than randomly distributed 1465 00:45:44,800 --> 00:45:46,320 ordered rather than randomly distributed what does that means that means that 1466 00:45:46,320 --> 00:45:46,330 what does that means that means that 1467 00:45:46,330 --> 00:45:49,140 what does that means that means that they are crystalline structures ordered 1468 00:45:49,140 --> 00:45:49,150 they are crystalline structures ordered 1469 00:45:49,150 --> 00:45:51,030 they are crystalline structures ordered in the solid means it's a crystalline 1470 00:45:51,030 --> 00:45:51,040 in the solid means it's a crystalline 1471 00:45:51,040 --> 00:45:57,540 in the solid means it's a crystalline structures okay now let's talk about 1472 00:45:57,540 --> 00:45:57,550 structures okay now let's talk about 1473 00:45:57,550 --> 00:46:00,450 structures okay now let's talk about this metallic bond in a little bit now 1474 00:46:00,450 --> 00:46:00,460 this metallic bond in a little bit now 1475 00:46:00,460 --> 00:46:06,089 this metallic bond in a little bit now remember again the metals are considered 1476 00:46:06,089 --> 00:46:06,099 remember again the metals are considered 1477 00:46:06,099 --> 00:46:12,450 remember again the metals are considered as if the positively charged metal atoms 1478 00:46:12,450 --> 00:46:12,460 as if the positively charged metal atoms 1479 00:46:12,460 --> 00:46:18,960 as if the positively charged metal atoms are placed in an electron sea and these 1480 00:46:18,960 --> 00:46:18,970 are placed in an electron sea and these 1481 00:46:18,970 --> 00:46:22,710 are placed in an electron sea and these electrons C are actually the valence 1482 00:46:22,710 --> 00:46:22,720 electrons C are actually the valence 1483 00:46:22,720 --> 00:46:26,720 electrons C are actually the valence electrons of the metal atom for example 1484 00:46:26,720 --> 00:46:26,730 electrons of the metal atom for example 1485 00:46:26,730 --> 00:46:29,400 electrons of the metal atom for example sodium if you consider the sodium sodium 1486 00:46:29,400 --> 00:46:29,410 sodium if you consider the sodium sodium 1487 00:46:29,410 --> 00:46:31,680 sodium if you consider the sodium sodium has one valence electrons so if you look 1488 00:46:31,680 --> 00:46:31,690 has one valence electrons so if you look 1489 00:46:31,690 --> 00:46:34,349 has one valence electrons so if you look at the structure crystalline structure 1490 00:46:34,349 --> 00:46:34,359 at the structure crystalline structure 1491 00:46:34,359 --> 00:46:36,599 at the structure crystalline structure of the sodium it would be something like 1492 00:46:36,599 --> 00:46:36,609 of the sodium it would be something like 1493 00:46:36,609 --> 00:46:39,650 of the sodium it would be something like this you have the sodium plus charged 1494 00:46:39,650 --> 00:46:39,660 this you have the sodium plus charged 1495 00:46:39,660 --> 00:46:42,450 this you have the sodium plus charged ions like this and you have the electron 1496 00:46:42,450 --> 00:46:42,460 ions like this and you have the electron 1497 00:46:42,460 --> 00:46:44,849 ions like this and you have the electron cloud and these electrons are 1498 00:46:44,849 --> 00:46:44,859 cloud and these electrons are 1499 00:46:44,859 --> 00:46:46,770 cloud and these electrons are delocalized that means they move all 1500 00:46:46,770 --> 00:46:46,780 delocalized that means they move all 1501 00:46:46,780 --> 00:46:52,020 delocalized that means they move all over the solid sodium and now why the 1502 00:46:52,020 --> 00:46:52,030 over the solid sodium and now why the 1503 00:46:52,030 --> 00:46:58,380 over the solid sodium and now why the metal simply accepts or forms this kind 1504 00:46:58,380 --> 00:46:58,390 metal simply accepts or forms this kind 1505 00:46:58,390 --> 00:47:00,990 metal simply accepts or forms this kind of structure the reason is because the 1506 00:47:00,990 --> 00:47:01,000 of structure the reason is because the 1507 00:47:01,000 --> 00:47:05,130 of structure the reason is because the metals do not have enough valence 1508 00:47:05,130 --> 00:47:05,140 metals do not have enough valence 1509 00:47:05,140 --> 00:47:08,880 metals do not have enough valence electrons to make octet rule to make 1510 00:47:08,880 --> 00:47:08,890 electrons to make octet rule to make 1511 00:47:08,890 --> 00:47:13,380 electrons to make octet rule to make bonds with the other metals so in order 1512 00:47:13,380 --> 00:47:13,390 bonds with the other metals so in order 1513 00:47:13,390 --> 00:47:16,920 bonds with the other metals so in order to get the highest sharing of the 1514 00:47:16,920 --> 00:47:16,930 to get the highest sharing of the 1515 00:47:16,930 --> 00:47:18,440 to get the highest sharing of the valence electrons 1516 00:47:18,440 --> 00:47:18,450 valence electrons 1517 00:47:18,450 --> 00:47:22,410 valence electrons they simply form a structure like this 1518 00:47:22,410 --> 00:47:22,420 they simply form a structure like this 1519 00:47:22,420 --> 00:47:26,880 they simply form a structure like this and this way all the valence electrons D 1520 00:47:26,880 --> 00:47:26,890 and this way all the valence electrons D 1521 00:47:26,890 --> 00:47:29,609 and this way all the valence electrons D localizes and they belong to all of the 1522 00:47:29,609 --> 00:47:29,619 localizes and they belong to all of the 1523 00:47:29,619 --> 00:47:32,400 localizes and they belong to all of the positively charged metal atoms this 1524 00:47:32,400 --> 00:47:32,410 positively charged metal atoms this 1525 00:47:32,410 --> 00:47:35,880 positively charged metal atoms this actually increases the sharing of 1526 00:47:35,880 --> 00:47:35,890 actually increases the sharing of 1527 00:47:35,890 --> 00:47:38,579 actually increases the sharing of electron between the metal ions that 1528 00:47:38,579 --> 00:47:38,589 electron between the metal ions that 1529 00:47:38,589 --> 00:47:41,970 electron between the metal ions that means it increases the bond strength the 1530 00:47:41,970 --> 00:47:41,980 means it increases the bond strength the 1531 00:47:41,980 --> 00:47:44,760 means it increases the bond strength the more electrons shared the stronger the 1532 00:47:44,760 --> 00:47:44,770 more electrons shared the stronger the 1533 00:47:44,770 --> 00:47:47,520 more electrons shared the stronger the bonds as a matter of fact all metals 1534 00:47:47,520 --> 00:47:47,530 bonds as a matter of fact all metals 1535 00:47:47,530 --> 00:47:49,530 bonds as a matter of fact all metals except few of those are solid at room 1536 00:47:49,530 --> 00:47:49,540 except few of those are solid at room 1537 00:47:49,540 --> 00:47:51,210 except few of those are solid at room temperature what does that means that 1538 00:47:51,210 --> 00:47:51,220 temperature what does that means that 1539 00:47:51,220 --> 00:47:53,190 temperature what does that means that means that the metallic bond which is 1540 00:47:53,190 --> 00:47:53,200 means that the metallic bond which is 1541 00:47:53,200 --> 00:47:54,270 means that the metallic bond which is the 1542 00:47:54,270 --> 00:47:54,280 the 1543 00:47:54,280 --> 00:47:56,400 the electrostatic attraction between this 1544 00:47:56,400 --> 00:47:56,410 electrostatic attraction between this 1545 00:47:56,410 --> 00:47:59,040 electrostatic attraction between this electron cloud and positively charged 1546 00:47:59,040 --> 00:47:59,050 electron cloud and positively charged 1547 00:47:59,050 --> 00:48:02,370 electron cloud and positively charged metal ions is pretty strong and they 1548 00:48:02,370 --> 00:48:02,380 metal ions is pretty strong and they 1549 00:48:02,380 --> 00:48:06,780 metal ions is pretty strong and they keep the metal together but now if you 1550 00:48:06,780 --> 00:48:06,790 keep the metal together but now if you 1551 00:48:06,790 --> 00:48:10,260 keep the metal together but now if you look at some of the properties of the 1552 00:48:10,260 --> 00:48:10,270 look at some of the properties of the 1553 00:48:10,270 --> 00:48:14,130 look at some of the properties of the metals for example look at how the 1554 00:48:14,130 --> 00:48:14,140 metals for example look at how the 1555 00:48:14,140 --> 00:48:18,780 metals for example look at how the mountain points changes as you go from 1556 00:48:18,780 --> 00:48:18,790 mountain points changes as you go from 1557 00:48:18,790 --> 00:48:22,770 mountain points changes as you go from left to the right in 3-d or 4d in the 1558 00:48:22,770 --> 00:48:22,780 left to the right in 3-d or 4d in the 1559 00:48:22,780 --> 00:48:23,310 left to the right in 3-d or 4d in the d-block 1560 00:48:23,310 --> 00:48:23,320 d-block 1561 00:48:23,320 --> 00:48:27,690 d-block what you expect that the more electron 1562 00:48:27,690 --> 00:48:27,700 what you expect that the more electron 1563 00:48:27,700 --> 00:48:30,630 what you expect that the more electron valence electron a metal will have there 1564 00:48:30,630 --> 00:48:30,640 valence electron a metal will have there 1565 00:48:30,640 --> 00:48:34,410 valence electron a metal will have there will be more electrons will be in this 1566 00:48:34,410 --> 00:48:34,420 will be more electrons will be in this 1567 00:48:34,420 --> 00:48:36,300 will be more electrons will be in this cloud and more electron in that cloud 1568 00:48:36,300 --> 00:48:36,310 cloud and more electron in that cloud 1569 00:48:36,310 --> 00:48:38,430 cloud and more electron in that cloud means as stronger attractions and that 1570 00:48:38,430 --> 00:48:38,440 means as stronger attractions and that 1571 00:48:38,440 --> 00:48:42,180 means as stronger attractions and that means a higher melting point but if you 1572 00:48:42,180 --> 00:48:42,190 means a higher melting point but if you 1573 00:48:42,190 --> 00:48:44,940 means a higher melting point but if you simply look at the melting points of the 1574 00:48:44,940 --> 00:48:44,950 simply look at the melting points of the 1575 00:48:44,950 --> 00:48:46,160 simply look at the melting points of the transition metals 1576 00:48:46,160 --> 00:48:46,170 transition metals 1577 00:48:46,170 --> 00:48:49,710 transition metals d-block from left to the right it 1578 00:48:49,710 --> 00:48:49,720 d-block from left to the right it 1579 00:48:49,720 --> 00:48:52,170 d-block from left to the right it increases and becomes maximum in the 1580 00:48:52,170 --> 00:48:52,180 increases and becomes maximum in the 1581 00:48:52,180 --> 00:48:55,500 increases and becomes maximum in the middle but when you have 5d electrons 1582 00:48:55,500 --> 00:48:55,510 middle but when you have 5d electrons 1583 00:48:55,510 --> 00:48:58,010 middle but when you have 5d electrons for example and then it decreases again 1584 00:48:58,010 --> 00:48:58,020 for example and then it decreases again 1585 00:48:58,020 --> 00:49:01,950 for example and then it decreases again this really cannot be explained with 1586 00:49:01,950 --> 00:49:01,960 this really cannot be explained with 1587 00:49:01,960 --> 00:49:05,160 this really cannot be explained with this model because you expect that more 1588 00:49:05,160 --> 00:49:05,170 this model because you expect that more 1589 00:49:05,170 --> 00:49:07,550 this model because you expect that more valence electrons means stronger bond 1590 00:49:07,550 --> 00:49:07,560 valence electrons means stronger bond 1591 00:49:07,560 --> 00:49:13,050 valence electrons means stronger bond right but that doesn't happens now in 1592 00:49:13,050 --> 00:49:13,060 right but that doesn't happens now in 1593 00:49:13,060 --> 00:49:16,580 right but that doesn't happens now in order to explain the metallic properties 1594 00:49:16,580 --> 00:49:16,590 order to explain the metallic properties 1595 00:49:16,590 --> 00:49:18,990 order to explain the metallic properties another theory came alone and that's 1596 00:49:18,990 --> 00:49:19,000 another theory came alone and that's 1597 00:49:19,000 --> 00:49:22,230 another theory came alone and that's called the band theory and the band 1598 00:49:22,230 --> 00:49:22,240 called the band theory and the band 1599 00:49:22,240 --> 00:49:28,020 called the band theory and the band theory as I will show you next time 1600 00:49:28,020 --> 00:49:28,030 theory as I will show you next time 1601 00:49:28,030 --> 00:49:32,340 theory as I will show you next time based on the formations of molecular 1602 00:49:32,340 --> 00:49:32,350 based on the formations of molecular 1603 00:49:32,350 --> 00:49:37,460 based on the formations of molecular orbitals which extend over all metal and 1604 00:49:37,460 --> 00:49:37,470 orbitals which extend over all metal and 1605 00:49:37,470 --> 00:49:40,290 orbitals which extend over all metal and the electron goes into the molecular 1606 00:49:40,290 --> 00:49:40,300 the electron goes into the molecular 1607 00:49:40,300 --> 00:49:42,480 the electron goes into the molecular orbital we will talk about that next 1608 00:49:42,480 --> 00:49:42,490 orbital we will talk about that next 1609 00:49:42,490 --> 00:49:45,840 orbital we will talk about that next time ok let's stop here now let me make 1610 00:49:45,840 --> 00:49:45,850 time ok let's stop here now let me make 1611 00:49:45,850 --> 00:49:49,530 time ok let's stop here now let me make an announcement Tuesday this coming 1612 00:49:49,530 --> 00:49:49,540 an announcement Tuesday this coming 1613 00:49:49,540 --> 00:49:53,970 an announcement Tuesday this coming Tuesday that will be what today is what 1614 00:49:53,970 --> 00:49:53,980 Tuesday that will be what today is what 1615 00:49:53,980 --> 00:49:56,640 Tuesday that will be what today is what twenty four twenty five twenty six 1616 00:49:56,640 --> 00:49:56,650 twenty four twenty five twenty six 1617 00:49:56,650 --> 00:49:58,800 twenty four twenty five twenty six twenty seven twenty eight twenty eighth 1618 00:49:58,800 --> 00:49:58,810 twenty seven twenty eight twenty eighth 1619 00:49:58,810 --> 00:50:02,790 twenty seven twenty eight twenty eighth of November Tuesday in the afternoon I 1620 00:50:02,790 --> 00:50:02,800 of November Tuesday in the afternoon I 1621 00:50:02,800 --> 00:50:06,810 of November Tuesday in the afternoon I will be available in my office to show 1622 00:50:06,810 --> 00:50:06,820 will be available in my office to show 1623 00:50:06,820 --> 00:50:07,849 will be available in my office to show you your 1624 00:50:07,849 --> 00:50:07,859 you your 1625 00:50:07,859 --> 00:50:10,190 you your papers exam papers so those who are 1626 00:50:10,190 --> 00:50:10,200 papers exam papers so those who are 1627 00:50:10,200 --> 00:50:12,019 papers exam papers so those who are interested to see their papers please 1628 00:50:12,019 --> 00:50:12,029 interested to see their papers please 1629 00:50:12,029 --> 00:50:15,019 interested to see their papers please come and see me in my office Tuesday 1630 00:50:15,019 --> 00:50:15,029 come and see me in my office Tuesday 1631 00:50:15,029 --> 00:50:15,799 come and see me in my office Tuesday afternoon 1632 00:50:15,799 --> 00:50:15,809 afternoon 1633 00:50:15,809 --> 00:50:19,160 afternoon Tuesday afternoon