we try to cover all possible geometries
actually and the angles by these
examples the next example I will work
out sulfur hexafluoride sulfur
hexafluoride if I write down the lewis
structure of sulfur hexafluoride it
would be again I follow and six electron
pairs around the central atom and six of
those are shared by the fluorines now
the number of electron pairs around the
central atom six electron pair geometry
is ophtho he drew octahedral and the
molecular geometry is also octahedral
remember again when you have no lone
pair electrons molecular geometry and
electron pair geometry or electron
domain geometry will be the same so
octahedral now how we draw that sulfur
here
now again remember if you should be able
to visualize I will advise you to
visualize these geometries tetrahedral
octahedral in your mind you should be
able to visualize that in this case
again this four of the fluorines are on
the corner of a square and this axis is
perpendicular to that you can actually
pick up any four they will make a square
there will be on the corner of the
square in the nocta he drew geometry so
you should be able to visualize all
angles are 90 degrees all angles are 90
degrees 90 degrees and they're all the
same the next example is boron
pentafluoride but no it's a bromium
pentafluoride sorry bromine
pentafluoride now in this case the lewis
structure again you count the number of
electrons valence electrons and the
Lewis structure write down the Lewis
structure and we have six electron pairs
around the central atom and five of
those are shared by five fluorines
terminal atoms like this this is bromine
and number of electron pairs around the
central atom six the electron pair
geometry is octahedral now the molecular
geometry again I take out one of the
terminal atoms from sf6 for example if I
take this right and the rest will be
square pyramid right the square
pyramidal geometry square pyramidal
Square
Pyrrha model pyramid Elle geometry now
the question here is let me just draw
the structure it would be again as
follow bromine fluoride fluoride
fluoride fluoride this is a square and I
have another fluorine here and this is
the pyramid how about the angles the
angles this angle here will be 90
degrees that angle all 90 degrees this
angle how about this angle would you
expect that this angle be less than 90
degrees or greater than 90 degrees that
means the angle between the actual
fluorine and the squared fluorine will
be less or less right why less because I
have a lone pair electron at the bottom
here right on this side here and that
lone pair electron will shift those for
fluorine bonding electron pairs closer
and it will be little less probably not
much but little less I should say less
than 90 degrees but not probably much so
again geometry is square pyramidal
geometry right now the next example
again xenon tetrafluoride and this is
xenon in the center again six electron
pairs if I make the Lewis structure
around the xenon central atom one two
three four five six and only four of
those are shared by four fluorine atoms
like this and how many electron pairs
around the central atom
six so the electron pair geometry
becomes octahedral
octahedral now how about the molecular
geometry now in this case consider that
octahedron so I will take out two of
those terminal atoms where do I take
them instead of them there's electron
pairs two electron pairs lone pair
electrons here for example let's see one
two three four or five no I have to take
one of those take that one for like this
so when you simply take two of those
then the geometry becomes square planar
just this square right Square planar
square planar geometry now what is the
molecular geometry again the xenon is in
the center and here I have perfect
square now all angle will be 90 degrees
now in this case remember there's one
electron pair here a bow this square
plane and one on the other side
so therefore this here is square planar
geometry that simply means all of those
five atoms one xenon four fluorines are
on the same plane and the fluorines are
corner of a square yes no in in this
case no we don't really because the
question is are these fluorines
considers as equatorial positions in
Oakland no in an optic adran since all
of the simply perfect octahedron since
all of the atoms if they are the same
atoms on the corner of an octahedron are
equivalent we don't really classify
those vertices as equatorial or axial no
in this case but if I go if I have two
lone pair electrons they will be one
above one below and the result is square
planar geometry okay I guess this is
all about I would say I must almost
consider covered all the possible
geometries from now on you should be
able to predict the geometry of a given
molecule or iron but provided that you
know how to write down the correct Lewis
structure start from there and go step
by step
and finally find out what is the
molecular geometry let's look at the
slides the slides have a similar type of
things I will just go those quickly this
is again molecular geometry remember
ammonia we have shown that and linear
electron domains these are the examples
that we worked actually all of those
like this now here is the case to show
you how the lone pair electron affects
the bond angle and remember we discussed
this again when you have a perfect
tetrahedron like in methane case all
angles are 109.5 exactly in the case of
ammonia less and that is simply pushing
down water is less I guess I call this
105 but it's one of 4.5 but very close
to that now here is another example
which shows how the double bond that
means two electron pairs shared between
the atoms which even though it's
considered as one electron pair in terms
of electrostatic considerations to find
the electron pair geometry but the angle
here you see again around the carbon
here I have three electron pairs or
three electron domains I should say now
the geometry is trigonal planar all
angle has to be 120 degrees but this
angle and that angle equal which is
greater than hundred and twenty this is
less why because now this two electron
pairs for the double bond occupy more
space andropause these bonding pairs and
makes the angle less than 120 right make
angle less than hundred 20 the octet
rule again 5 electron pairs we talked
about this now here is again the two
positions in trigonal bi-pyramidal
geometry now these two are axial
positions and these are equatorial
positions remember if we are going to
leave electron pair nonbonding electron
pairs around the central atom that it
has to be simply on equatorial positions
on these positions over here we talked
about that remember okay all of those we
worked out Orpah he drew all right here
is the question the question is what
happens if I have larger molecules can I
simply describe the geometry of larger
molecules similarly like I have done for
the molecules where where I have one
central atom and then we have all
terminal atoms to that right that was
the case I had one central atom and all
the other atoms are bonded to that those
are called terminal atoms simply but in
this case I don't have one central atom
or I can't really find out which one is
central this is acetic acid molecule
acetic acid molecule now these are
carbon here like this and then we have
the oxygens those are the oxygens and we
have the hydrogen's like this now we can
also predict or at least have an idea
about the shape of these larger
molecules by what we have to simply pick
out the central atoms a different part
of the molecule for example I can simply
pick this carbon as the central atom
here right in the first case now then I
will consider this part of the molecule
carbon and there are four atoms bonded
to carbon one of them is this carbon
here and
we have the hydrogen's now what is the
number of electron pairs around the
carbon four what is the electron pair
geometry tetrahedral what will be the
molecular geometry tetrahedral right now
this part here will be a tetrahedral the
angles will be one or nine point five
ideally but will it be one or nine point
five in this case for example this angle
here and this angle here no why because
I have three hydrogen's and one carbon
bonded to that central carbon atom right
it will be a little bit different angles
are not exactly 109.5 but the geometry
here around this carbon will be
tetrahedral I can easily call that
tetrahedral now how about this carbon
now right now in this case this carbon
how many electron pairs three electron
domains I should probably say right
three electron domains three electron
domains simply will give you electron
pair geometry trigonal planar and the
molecular geometry is also trigonal
planar but which atoms when I say
molecular geometry here this one this
one and this carbon and that carbon you
see now the angles here will be close
220 degrees not exactly twenty but we
have a double bond here right and the
others but again the geometry around
this carbon is trigonal planar geometry
right through you're no cleaner then
comes to the oxygen now if I write down
the Lewis structure you will find out
that the oxygen also has four electron
pairs around it but there are two lone
pair electrons so now I can simply guess
the geometry of this carbon this oxygen
and this hydrogen here and that will be
v-shape right so that angle will be less
than simply 109.5 less than perfect
tetrahedral so again you see by
combining these geometries around
different central atoms that I get up
right I can have an idea what would be
the geometry of this larger molecules I
can simply at least
get a notions about the relative
positions of all the atoms in this large
molecule right okay now here is the
polarity of the molecule how can we find
out whether the molecule will be a polar
molecule or a non-polar molecule right
and we have talked about the polarity
right remember polar molecule simply
have a dipole one side positive what's
aw I'm sorry negative but if I have only
diatomic molecules only diatomic
molecules there are two possibilities if
those are homo diatomic means the same
atoms the molecule will be nonpolar if
they are hetero diatomic the molecules
will be polar but what happens if you
have a molecule made of three atoms or
more than three four five six can we
find the polarity or predict the
polarity of the molecule and the answer
is yes how by using the molecular
geometry of that molecule if I know the
molecular geometry of the molecule and
if I know the bonds polarities each bond
polarity in the molecule I can find out
whether the overall molecule will be a
polar molecule or non polar molecule but
to find out the polarity of the molecule
polarity of a bond between two atoms
what do I need to know again to find the
polarity means which side positive which
side negative what do I have to know
electronegativity right
electronegativity if I know the
electronegativity of the two atoms
making a bond I can find out the
polarity of that bond the more
electronegative side will be the
negative Pole and the less
electronegative atom side will be
positive Pole and that way I can find
out the polarity of E
bunt now if I know the geometry by
adding these vectorial quantities of
dipole moments for each bunt I can get
the overall dipole moment vector
sometimes the dipole moment vector when
you add up all the vectorial properties
bump corresponding to the bond
polarities bond moments I should say you
may end up with zero overall factor in
that case the molecule becomes nonpolar
but if it is not zero the molecule will
be polar molecule polar molecule
now the actually let's let's take
examples like over here here is the one
case I guess these are okay fine
carbon dioxide right carbon dioxide so I
know that the carbon dioxide is a linear
molecule again two electron domains
right it's a linear molecule and I know
that each bond is polar bond and the
oxygen is more electronegative than the
carbon therefore the this side of the
bond will be little negative this side
will be little positive due to that I
will have a dipole moment vector
correspondent to this bond polarity
there right bond polarity now I have
another oxygen here and this bond is
also polar and I have also dipole moment
in this directions so when I add these
two vectors that means vectorial
addition will give me zero right so they
will cancel out so what does that means
in that case the molecule will be
nonpolar molecule or I can approach
differently again to predict the
polarity I can simply assign the partial
negative and partial positive charges
for each bond and this bond here partial
negative charge will be here Delta
negative right now this is Delta
negative and this is Delta positive
let's simply show that
now if the center of all negative
charges and the center of all positive
charges in a molecule coincide the
molecule becomes nonpolar even though
each bond is polar but if the center of
positive charges and the center of
negative charges do not coincide then
the molecule becomes polar molecule okay
now let's consider carbon dioxide I have
the oxygen and oxygen this is linear
again the geometry is important right if
it is not linear it's not going to be
nonpolar it will be a polar molecule
actually now so this bond is this is
Delta minus and Delta minus the same and
this is going to be Delta Plus over here
right actually
this Delta plus will be twice as much of
those anyhow so now let's find out the
center of negative charges the center of
this is negative this is negative the
center of negative charge will be right
here on the carbon right right in the
middle point here now how about the
center of the positive charge it's also
there on the carbon so what happened the
center of negative charges and the
center of positive charges coincided on
the same point they coincide so the
molecule becomes nonpolar right so this
is the rule that we will use nonpolar
but in order to be able to follow this
center of positive and negative charges
I have to know first I have to know the
geometry of the molecule second I have
to know the polarity of each bond show
those polarities and find out the center
of those positive and negative charges
now in the second case for water for
example
okay now in terms of vectorial quantity
as you see over here right this is a
polar bond and this side is negative
this side is positive so dipole moment
for this bond is this a vector in this
direction and now here also I have a
dipole moment for this polar bond and
this direction is a vector when you add
up those two vectors I will have this
resultant vector which is nonzero again
and it will just bisect this angle over
here therefore the molecule will be a
polar molecule so I can use those
vectorial additions actually to find out
the overall polarity or I can simply
find out the center of positive and
center at negative charges this is Delta
positive right and this part here is
Delta negative and this part here is
Delta positive and this part is now a
negative now let's find out the center
of positive charges center of positive
charge will be right in the midpoint of
these two hydrogen's there right now
center of negative charge son oxygen
what happened the center of positive and
negative charges now do not coincide
they are separated so what does that
means that means the molecule will be
polar molecule again if I show the
bacterial form of the dipole moment of
this molecule which is a polar molecule
and it will be in this direction here
bisecting the angle passing through the
oxygens right so that is the remember
again only polar molecules will have
dipole moments dipole moments but the
net overall simply molecule should be a
polar molecule the bonds may be polar
but the overall molecule may not be
polar as I showed you over here okay our
guess now let me just give you another
example let's consider carbon
tetrachloride
like this now the geometry of carbon
tetrachloride is perfect tetrahedral
carbon here all angles are again 109.5
exactly and this is the tetrahedral
shape and in the center of this
tetrahedron not have the Corbyn right
now are the bonds polar yes
now chlorine atom side will be negative
and the carbon part is positive so each
bond actually has a dipole moment vector
and this fat no out going from carbon to
this side negative and that's also out
there now when you add up those four
vectors you end up with zero resultant
vector right and the molecule is
nonpolar or you can see it as follow to
what is the center of the negative
charges in this molecule it will be
right in the middle of the tetrahedron
means where I have the carbon where is
the center of the positive charge it's
only on carbon so you see again centre
of positive and centre of negative
charges coincide
that means the molecule will be nonpolar
right so this is a non-polar molecule
non-polar molecule now let's consider
the chloroform I have three chlorine and
one hydrogen right now what is the shape
the shape would be again as follow I
have let's say chlorines here and
hydrogen's is here like this now each of
these bonds will be polar bond and Delta
negative here and Delta positive here
Delta negative Delta negative and now
when you consider this this bond here
the electronegativity of carbon is
little bit more than the
electronegativity of the hydrogen so
that means that this part would probably
be Delta I have to say here Delta Prime
because these deltas are all the same
amounts but this will be different
whatever it will be a little bit Delta
minus no Delta plus here and Delta minus
here Delta prime minus here now if I add
all of these vectors it is very similar
to this actually but in this case all of
the vectors that means dipole moments
correspondent to the bonds are equal
therefore they cancel out each other
when you add them up but in this case
they are different right three are the
same one is different when you add up
all these vectors due to that difference
the net resultant vector will not be
zero right what does that means that
means the molecule will be polar
molecule right polar molecule so we have
to consider actually the geometry and
also the bond polarities to predict
correctly whether the molecule will be
polar or nonpolar molecules
okay now the next topic again in this
chapter is valence bond Theory now in
chemistry there are several different
theories which explains the bonding in
molecules between atoms and also the
structure of the molecule right and in
this case in this chapter we will just
talk about two of those and the first
one is valence bond Theory Islands bunt
theory and the second one is called
molecular orbital theory molecular
orbital theory this is simply
abbreviated as mo theory and this is
everywhere this valence bond Theory
as follow okay
now what are these theories how they
explain the abundant between the atoms
in a molecule
now the valence bond Theory simply says
that the bond between two atoms will
result from the overlap of the two
atomic orbitals from these two atoms
which contains one electron each and
this way when the atomic orbitals
overlap then the electron comes out from
each orbital pair up and shared between
the atoms and we end up with a bond a
chemical bond this is what how the
valence bond Theory defines or explains
the chemical bond between two atoms
overlap of the atomic orbitals right
overlap of the atomic orbitals
now what atomic orbitals
would they be actually atomic orbitals
which simply holds the valence electrons
right it has to be the valence electrons
valence electrons you're talking about
remember in a chemical bond always the
valence electrons are involved right
shared or transferred from one atom to
the other core electrons are never been
involved now very simple case here for
example the example the bond between two
hydrogen atoms in a hydrogen molecule is
explained by the overlap of the 1s
orbital on these two hydrogen and like
this and it says that the electron that
comes out from these two orbitals from
these two hydrogen's pair up here they
have to pair up that means that spin off
one electron is up the other one will be
down
that's what para means again the
electron density if you look at the
electron density probability of finding
the electron it will be higher between
the two nuclei that means the electrons
were sort of concentrated between the
two nuclei which means that they share
the electron this is the valence bond
theory so this is two hydrogen atoms
form in the hydrogen molecule how about
the hydrogen chloride now in the
hydrogen chloride again you see remember
if you write down the Lewis structure of
the chlorine 17 electrons the valence
orbitals are 3s and 3p and 3s and 3p
let's say for chlorine in case 17
valence shell 3s and 3p 3s2 3p5 so you
simply take one of this orbital p
orbital which has one electron one p
orbital so the valence bond Theory says
that the chlorine uses this p orbital
which contains one electron and over
with the atomic orbital of the other
atom forms a chemical bond like the case
in hydrogen chloride 1s orbital of
hydrogen which contains one electron
remember and then two three P one of the
three P orbitals on chlorine valence
orbital remember these will be always
valence orbitals they will overlap this
fashion and a bunch simply will form and
two electrons that shared are paired up
here and they spend more time between
the hydrogen and the chlorine nuclei
between there now when it comes to the
chlorine molecule the bond between two
chlorine atoms in a chlorine molecules a
single bond again the valence bond
Theory says each chlorine has that one
3p orbital which has one electron and
those three P orbitals on two chlorines
overlap in this fashion head-on form
this is the head-on overlap simply had
to had a type of overlap and then the
electron that one electron coming from
this 3p and one electron coming from
that 3pc me from that chlorines shared
and they pair up here
right there and the bond simply forms
this is how the valence bond Theory
simply explains the bonding again now
this simply shows how the bond distances
are simply formed or I should say
determined because when the two atoms
are too close to each other as they
overlap the orbitals then they start
repelling each other because the two
nuclei pause the fighters will repel
each other so the minimum energy here
corresponds to the bond distance for the
hydrogen atom for every bump as that
bond distance which corresponds to the
minimum energy or minimum repulsions of
the two atoms as a matter of fact but
the question here is the bonding is okay
but how about the shape of the molecule
how does the geometry of a molecule can
be predicted by using valence bond
theory this overlap model overlap off
the atomic orbitals let's take the
examples and show you how it works now
for example suppose that I react carbon
with hydrogen like this now let's
remember the carbon as 1s 2 2 s 2 and 2
P 4 2 P 2 electrons right simply six
atomic number of six six electrons now
the valence bond theory says that the
atom uses the valence orbital which
contains one electron to overlap and
form the bond with the other atoms so
what we expect that the carbon 3 these
are 2 P orbitals 3 of them have one
electron each like this so now it can
uses these two elect orbitals which
contain one electron and overlaps with
the hydrogen 1s to form a compound so if
you use purely valence bond Theory
approach and predict what will be the
compound between the carbon and hydrogen
reaction between carbon and hydrogen you
expect to form CH 2 right simple why
because the carbon simply has two P
orbitals which contains one electron
each remember that P orbitals are
perpendicular to each other right they
are perpendicular to each other three of
the P orbitals
in Xyz directions now one hydrogen will
come out from this side and overlap and
uses that electron coming from the 1s
orbital pair up and another hydrogen
will come out from this directions and
it will also overlap 1s orbital its 1s
orbital with the P orbitals and as a
result I will have or I should have a
ch2 molecule and what should be this
angle if I have a ch2 molecule for
example what should be the angle
according to the valence bond Theory 90
right why 90 because the P orbitals are
perpendicular to each other all three P
orbitals now to get the maximum overlap
again the hydrogen will simply approach
from this direction here and this will
approach from that direction that will
be 90 degrees right 90 degrees but there
is a problem here the problem is when
you react carbon with hydrogen it
doesn't form ch2 molecule but it forms
ch4 right so actually not this but I
have ch4 hmm and now what's the
structure a little bit you know hard to
predict using the pure valence bond
Theory simply using that overlap model
of the atomic orbitals for the
formations of the bond between the two
atoms now we can have we have more
examples of that we can give more
examples which simply the valence bond
Theory has problem to explain
particularly the structure of the
molecule now in that case actually the
product I mean if you use the valence
bond Theory you say okay two carbons has
two P orbitals one electron in each and
those will overlap with the hydrogen 1s
orbital to form the bond
therefore the compound should be ch2 but
it's not now the other case is consider
the reaction let's say between the
hydrogen and the oxygen now the oxygen
again has two P orbitals four electrons
in those two P orbitals this is two P
orbitals right
hydrogen has one s simply and one
electron there this hydrogen one
electron there one s orbital
okay you can say alright this hydrogen
uses this one s orbital one electron
overlap with one of the P orbitals of
the oxygen form a bond
right oxygen hydrogen bond now the other
second hydrogen will overlap with this
one and form a bond yes that's true
as a matter of fact we expect that the
product here has to be h2o and it is h2o
but the problem is this now
since the oxygen exactly same as that
carbon uses the 2p orbitals which are
perpendicular to each other right this
is one electron there and one electron
there those 2p orbitals are
perpendicular to each other no that too
like to me this is hydrogen's then the
simply the hydrogen will come from this
direction and overlap the 1s orbital and
the electrons pair up and other hydrogen
comes from that there and overlap and
this way the bond forms what will be
this structure the geometry of the water
molecule one hydrogen here one hydrogen
there how about the angle it has to be
90 degrees right why because 2p orbitals
are perpendicular to each other and to
overlap actually with the hydrogen's
those two P orbitals are used then this
should be 90 degrees but in reality we
know that that's not 90 degrees but what
is it 105
104.5 that's right degrees hmm so that
is the problem and now we can simply go
further actually and take the nitrogen
again and reacted with hydrogen right
then guess what will be the compound
between the nitrogen and the hydrogen
now let's consider the orbitals on the
nitrogen that will be used to make
overlap according to the valence bond
theory and form a bond with the
hydrogen's there are three electrons in
two P orbitals of the nitrogen what does
that means each of those will overlap
with the hydrogen 1s orbital form a bond
therefore I expect that the compound
will be nh3 yes actually the compound is
nh3 how about the geometry bond angles
now again with this approach since 3p
orbitals are used the the angles here
should be all 90 degrees actually this
will be up here like this right 90
degrees why because these are P orbitals
all P orbitals are perpendicular to each
other so we expect that it should be 90
degrees but this is not 90 degrees all
of those what is the angle angle is 107
degrees hmm so there is a problem right
a problem and the problem of what
problem of explaining the geometry of
the molecules and also sometimes problem
of predicting what will be the product
right like in the case of carbon and
hydrogen so the valence bond theory
proposes a hybridization in fact for
explaining the geometry of the molecule
now what is hybridization hybridization
is actually
mixing the atomic orbitals on the
central atom and forming new orbitals
which is a mixture of yeast contains
some part from the mixed atomic orbitals
and those orbitals are called hybrid
orbitals hybrid orbitals and now it says
that the hybrid orbitals the valence
bond Theory points toward the direction
in which the repulsion between them will
be minimum what is that means that means
is this if you have two hybrid orbitals
around the central atom it currently the
valence bond theory we will see what the
hybrid orbital means those each hybrid
orbitals if I have two will simply be on
linear fashion one is shown in this
direction the other was shown in that
directions simply 180 degrees between
them so if those hybrid orbitals and
again the valence bond Theory says now
the bonds between the atoms are formed
by overlap of the hybrid orbitals of the
central atom and the atomic orbitals of
the terminal atoms right and since the
hybrid orbitals will be just the same in
in terms of positions depending on the
number of hybrid orbitals will be just
the same as the lone pair electrons or
electron domains that we have described
before their positions will be just the
same as the electron pairs around the
central atom so since they simply they
are used to make a bounce by overlapping
with the terminal atoms so the positions
of the terminal atoms will also be
determined by the directions of these
hybrid orbitals so it will end up the
same geometries that we predicted by
using valence bond electron pair EPR
electron valence valence electron
electron pair repulsion paler shell
electron pair repulsion that model that
we use is called valence shell electron
pair repulsion so
we will have the geometries in fact
predicted by the hybrid orbital approach
of the valence bond Theory same as the
valence shell electron pair repulsion
theory of VSEPR now let's let's see how
this hybrid orbital simply forms let's
simply consider the reaction between
beryllium and fluorine hmm
this case this is actually worse because
now if I write down the loose truck the
electron job electron configurations of
beryllium I will have this 1s2 2s2
hmm the point is William does not
contain any orbital which contains one
electron so that it will overlap and
form a bond right so what how come the
compound forms and we know that the
compound here forms and it is bf2 how
can we explain what are the orbitals
that are used to bond between simply to
form the bond between the beryllium and
fluorine actually barium and fluorine
this is going to be B II actually
beryllium like this okay it goes as
follows the valence bond Theory says all
right I have the beryllium electron
configurations as 1s 2 + 2 s 2 now I
have here 2 P but there is no electron
here right and says I move one electron
from the 2 s 2 2 P right and this
requires energy actually and let's try
to show how that simply happens I have
two electrons here this is 2 s right
these are 2p no electrons there and P
and now I just move one electron there
and then at the end I have simply this
one s + 1 P electron this is s this is P
electron simply mixed and then I also
have here two more P orbitals which are
not involved in a mixing this is also
true P and this is 2 s over here like
this
now the valence bond Theory says these
two orbitals are mixed to form two
hybrid orbitals
what kind of Schaben is the hybrid
orbital does it look like p orbital does
it look like an S orbital actually it is
sort of a mixture of two the hybrid
orbitals that would be obtained from
here is called SP hybrid orbitals hybrid
orbitals and they will simply have a
shape as follow here is the beryllium
and the hybrid orbitals this is a big
part here a small part here this is the
hybrid orbital and what hybrid orbital
this is the SP hybrid orbital now the
rule here is the number of atomic
orbitals that you mix to form hybrid
orbitals will be equal to the number of
hybrid orbitals that you end up at the
end and if I apply it for this case I
mix up two atomic orbitals and I have to
end up with two hybrid orbitals and
these hybrid orbitals are SP hybrid
there are two SP hybrid orbitals one of
them is like this where is the other one
the other one is again it says to get
the minimum repulsion it will simply
point in this direction and then there
is a little part here but usually we
don't really think about those little
parts now I have two hybrid orbitals and
now how many electrons will go there two
electrons right now actually these two
electrons there that the electron that I
transferred here one electron will be
here and one electron will be here now I
have simply a picture which shows the
two SP hybrid orbitals on beryllium on
the same line actually to get the
minimum repulsion slide 180 degrees
between now this is ready to make
overlap with the fluorine P orbitals and
the fluorine P orbitals
remember on the fluorine there is one p
orbital which contains one electron
right and that will overlap with this
like this and electron will pair up and
another fluorine that will overlap with
this let's put that here again remember
the P orbitals has this shape right this
and as a result fluorine this fluorine
this perineum and that fluorine will be
on the same line because to get the
maximum overlap actually and the
geometry of beryllium fluoride will be
linear this is the explanation of the
geometry used by valence bond Theory
write the orbitals overlap and but again
the orbitals on the central atom are
hybrid orbitals hybrid or business clear
now if I go to the next example
for the ch4 molecule remember this ch4
molecule carbon again if I write down
the electron configuration 1 s 2 and 2s2
2p2 like this let's show it here this is
the 2's and now the 2p orbitals like
this and two electrons here again the
valence bond Theory sells this electron
is simply moved from here to there then
I simply have will mix up these orbitals
actually this one s orbital than 3p
orbitals and obtain hybrid orbitals each
of these are SP 3 hybrid orbitals hybrid
orbitals now again where this 3 comes
that 3 here indicates that 3p orbitals
are mixed and 1s orbitals are mixed so
this shows you that therefore atomic
orbitals are mixed to form sp3 hybrid
orbitals how many hybrid orbitals four
hybrid orbitals and each of these four
hybrid orbitals will simply direct to
the corner of a tetrahedron around the
carbon atom to get the minimum reports
and they have one electron each and this
way they will overlap with the hydrogen
1s orbital to form carbon hydrogen bonds
how many four of those what will be the
structure tetrahedral right
since the hybrid orbital shows the
tetrahedral so let's show it here this
is let's say one of the hybrid orbital
and now I have another hybrid orbital
here in other hybrids and another hybrid
here like this these are all remember
equivalent even though they look like
different size but they're all the same
size now how
electrons I have four I will put those
four electrons here like this okay and
now this is again the tetrahedral
showing to the corner of a tetrahedral
vertices of a tetrahedral four
hydrogen's will come from each side and
by overlapping with the s one s orbital
and I have ch4 molecule and the
structure will be tetrahedral molecule
like this all angles here are 109.5
degrees tetrahedral molecules like this
clear now each of the orbitals that are
used are SP three hybrid orbitals how
many four because I mixed four atomic
orbitals and I end up with four hybrid
orbitals now for the case of water for
example let's see oh the time is over I
guess right okay I guess I have to stop
here so we will continue Thursday right
I forgot to give you the attendance
sheet but