Video: Valence Bond Theory Video Lecture | Chemistry Class 12 - NEET

Hello Friends in the previous lecture we have
talked about that how equivalent Bond is formed
and we see the whole chapter is
basically meant for valence Covalent Bond
and more especially so now we are
going to talk about the new theory that
is Valence Bond theory and so what is Valence
Bond theory and it is very important
for us to understand that because this
detail on this theory gives us various
details about how equivalent Bond is form
so before understanding the
Valence Bond theory be sure to send the
postulates of Valence but what is
actually one theory actually very
smoothly gives us the detail of the
direction of the orbitals which a
particular valence shell consists of and
obviously if we know that a valence
shell consists of Venus orbits might be
SPT or F so during the bond
formation with other atoms they are
forming a kind of direction so that is
the reason that they'll make a
particular angle or they will have a
particular geometry so this all are the
details that could be explained with the
help of the variance for T V so let us
understand the postures of it and let us
understand it each of it one better so
talk about the first one that is equal
part is for only meant the half filled
orbitals of the two atoms overlap each
of them so this is the first point that
we are going to talk to and this is the
most fusion one so if you are talking
about the noble gases so the noble gases
doesn't mess it up an unpaired electrons
all the electrons that have been present
in its valence shell it has been
completely occupied so we see it is
already fulfilled and there is no chance
of formation of if we see an unpaired
electron so that season that noble gases
doesn't forms bond with the amine in the
component we're talking about the Saudi
event marine chlorine consists of BC one
unpaired electron really sort of motion
so it makes me view that also so if I
draw the structure of qualify represent
the structure of glowing 17 so I could
get it is can be written as that is 1s2
2s2 2p6 3s2 3p5 so since we are talking
about orbitals and not the orbit so that
what this is
the all right and that is be already a
piece of shit so p subshell consists of
three or mittens and as it consists of
high electrons so therefore this is 1 2
3 that is this is 4 F 5 so in this case
this easy at all but it consists of one
very electron and that's the reason that
you it is capable of swapping the one
with end of any that is sodium element
this is the atomic number 11 so then why
would I need s 1s2 2s2 2p6 3s1 so
talking about the last shell and that is
the third shell it consists of 3 s
orbitals and just 3 s already consists
of only one electron so this is
unpatented run and even this is
unfinished on so now they really have
the capability for forming a bond so
this is what the first point is and this
is the detail that we are just talking
about this theory so this is the first
one that we have what you know that is a
covalent bond is formed only then the
half filled orbitals from the two atoms
who connect each other so this is the
first electron to move
ok more the next one so this again
points is that each overlapping at
atomic orbital should contain an
unpaired electron with opposite spin so
that is what I have explained with help
of this angle so suppose this is NaCl
and the wood are deforming suppose
actually this will be I think what that
we are talking about but to suppose it's
what I'm talking about like X here so
HCl is the one which is easily
having in 1s1
so because just of one unpaired electron
so now H and Cl they both can form one
with each other and because we have no
keyboard especially here at bokya board
anymore so
but during overlapping the both the
electrons should be of opposite to speed
means one should be also plus s plus
office meanwhile the other one should be
off minus half spin and then only the
bonding takes place so this is the
second point that I may have mentioned
about it and talking about the next one
that is the overlapping or atomic
orbital must have nearly the same energy
so this is also the main point that we
are going to talk about but yeah talking
about the that sets in soapy water
middle consists of basically a
particular energy in fact every orbital
consists of a particular energy but
really a molecule or only a pod is been
formed when a particular atom which has
a particular valence orbital that for
myself that of the other append electron
then which is belonging to a particular
orbital
so if the both have almost the same
energy they're only the mod will happen
and this is what it is talking about
that is developing atomic orbitals must
have nearly the same energy so that is
it asking for my twins here but even
though the boilerman digit is been
altered but while talking about the
carbon and hydrogen we'll talk about it
with him so carbon has an automotive p
orbital emanate off the hydrogen it has
not a motion of s all kind of motion
which consists of s orbital and that s
orbital come s with that of the BR mind
a lot of the that is carbon and then and
that's the reason that it forms that the
bonding carbon and hydrogen this is the
third one that I would experiment so
talking about the next point that is the
fourth point the electrons can get
neutralized and the electron gets better
obviously and one will be of opposite
spin off both of them is of opposite
spin means one place of positive half by
the end come and we have a negative half
value suppose so if the both we combine
obviously they will utilize each other
and that is what it is talking about
that is the electron spins can utilize
and electrons get paired up as they're
really the economy get better so this is
what I want to explain it is suppose I'm
talking about hydrogen in fact CF so
whenever the hydrogen and this is the
thing that I'm talking water when the
overlapping happens so this is the
orbitals where we would see the morning
we'll take Springs so suppose this is
the one which is off hydrogen which is
of having plus s or s is used to having
a plus 1/2 charge
when I sell value my talking work that
the chlorine shall have you see negative
husband so if you combine this two it
will neutralize and that is the reason
that we will see that the overlapping
also can takes place and you cannot see
the orbitals which is having the same
spin this is never observe that is what
the point for that as one have to talk
about and it is more to the next point
so now let us move on to the next point
that is doing overlapping of atomic
orbitals electron density increases
between the two nucleus or to declare
and therefore the repulsion within the
nuclear decreases obviously we know that
during the word formation obviously two
atoms will combine with each of them and
so as to form a more but it is not only
the Olympus the they will combine with
each other or they will share the
electrons it is not the atom that we
share the electrons but during the
formation of the board of this C or
during the interaction obviously the
nucleus of an atom can be attracted
without in the nucleus of the atom so in
this case B place is the one who sends a
positive charge by the other this is
also which consists of a positive charge
so interacting it they will feel a
repulsion force so search the propensity
that because men every mode forms we
know that the valence electrons are and
wouldn't that are being able to form a
bond and that is the reason or the earth
pair electrons they are able to for me
more thatís the reason do the mod
formation even the difference or the
repulsion between the nucleus has a
nucleus of the two atoms they will get
reduced and that is how the interaction
start takes place while the nucleus will
have an attraction towards the electron
of the other atom why is the electron
will have the attraction towards the
other nucleus so therefore the
attractive force of what or we can say
more attractive force you can observe
and you say that as it approached it
will be reduced and this is how the bond
formation takes place and talking about
the next one that is yes you mean this
actually bond formation and this you
spitting list obviously when two atoms
they will collide with each other they
combine with each other energy police
and this indicates that the more the
energy will be released then the mod
formation will be more and the formal
the poor will be so it depends all the
thing that is what we are going to talk
about in the next topics or next
so let us talk about the sixth point so
the six months is that Edie bond is for
at equal distance when the system has
minimum potential energy and makes
instability so this is what I want to
explain so if what is been afforded in
distance suppose if the two atoms are
having the same kind of
electronegativity what we can find it as
they have the atomic orbitals occupied
again
okay models they have suppose the same
energy then we could see that there will
be having a minimum for energy and
maximum stability they would acquire
maximum stability Edessa reason that is
the reason that they are forming the
bond and that makes the bond to be more
stronger and more attractive or to hold
the two atoms and this is what the
system oint is and let us talk about the
next one that is that is the seventh
point and it says that the strength of
the polar bond depends upon the extent
of overlap of orbital between the two
atoms obviously the quad will be more
stronger it will depend on the extent in
which the two orbiters two orbitals
means of two different items they
combine with each other so the more the
overlapping then we could say that both
the stronger the bond would be and that
is the reason that this before with
stronger pot and the interaction between
and the two atoms will be more it
supposed to break it it will look at
moving energy and it will depend on how
they are oriented or how they are
overlapping
even though overlapping of the two times
and its let alone that again this
head-on collision we could say so you
know that depends on that thing so these
are the things that we are going to talk
about the previous then we will talk
about in the next lecture and let us
talk about the next point that is the
eight points is that the number of foil
bond formed by an atom of an element is
equals to the number of unpaired
electrons present level etc obviously by
simple if I am talking about the third
carbon has n valence electron or four
and that is the reason it forms for
point rate is not necessary because
talking about the nitrogen nitrogen also
has 5 electrons or two Michelle but if
that case not all of the fire only three
of the one which are forming the bond
and that is the reason that you're
talking about Ln one so that is the
thing
and let us move on with the next one so
now let us move on to the next point and
the next one says that each other make
an orbit except S orbital has a
particular direction in space so that is
what I am talking about so that is
talking about the S often is s 1 but it
has a produced a man that is spherical
and looking for the P orbitals
Fiorella's have deceived ownership at
their PC divided into px orbital PR PZ
orbital and talking about D and F also
they have put if you shape on the
particular that is naturally which they
are we need more so talking about the S
orbitals they don't have any kind of
addition and that's the reason that this
vbt or valence bond theory is basically
related to the actions that are being
shown by the orbitals s P me at F and
talking about the orbital every output
has its own axis of own axis of
direction that we could say so this is
the 9.10 curve would talk and talk about
the application of this we are going to
make an application that how it is being
applied in actually the bond formation
so this is what we also we are going to
talk about so one go to the next one
that is the ten point and it says that
the geometry of the molecule is decided
by the direction fashion orientation of
the overlapping of orbitals obviously
that is a the geometry of a molecule
methane would be planar planar structure
or whether it would be you say trigonal
planar a trident
so this all kind of structure actually
this will depend it will depend on the
basically the direction of the orbitals
so if we are talking about the ordinary
mortals that is 21 X here so H is the
one which has s orbital and doing this
has p orbital so s has no - unit on it
so it is not it is say no direction in
orbit so that is the incident it came
from my with any of the P or bring in
any tension and the more we love them
but talking about the methane methane
will obviously it will have a pretty
good I should agree
combined with that of a die should be
that of the hydrogen when talking about
that of the Ethan so in that case the
direction also matters and that's the
reason that if our carbon double bond a
speed now setting so that also plays a
very vital route and
to show the geometry of the molecule so
there are few topics that we are going
to talk about and the application of it
so these are the three exams then I was
talking about so thank you friends for
watching this video I hope you
understood this very clearly important
is what is actually - one theory and I
will share this video if the Fed said
it's from Vegas of their weakness thank
you so much
you