Video: Molecular Orbital Theory Video Lecture | Physical Chemistry for NEET

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watching the video please make sure you
have watched part 1 - Part 3 6 let's
start with the molecular orbital Theory
the last Theory the question is why do
we need to study this theory we already
have so many Theory we have learned the
latest theory we have learned the Vesper
theory we have learned the valance board
theory right so many theories we have
learnt why do we need molecule orbitals
see if you see the oxygen if you take
this oxygen in the lab and
experimentally you see oxygen is
paramagnetic this is a liquid oxygen and
get attracted towards laniel so oxygen
is param param Agni experimentally this
is true but in the existing model we
could not explain why this paramagnetic
and also if you see H to exist but H it
doesn't exist you don't have answers for
all these you don't have answers for the
chemical properties of the molecules or
these we need molecular orbital theory
so to answer these questions will study
molecule orbital this theory was
developed in 1932 and the fishes of the
story are it says that electrons in the
molecules are present in various
molecular orbitals see the whole
perspective is different in this case
the other theories talks about atoms and
the overlap this theory says that if I
have a molecule and view molecule as one
piece the way we have orbitals in atoms
we have orbitals and molecules so in
this case the wave aaalac euler orbital
theory works is it considered molecule
as one entity right and all the rules
more vague most of the rules which we
have our items
the similar kind of rules applies here
for molecules
please note so you have viewing
molecules as two different atoms it
views molecules as molecules itself and
the molecules see the way Adams has
orbitals right adam has orbitals and all
this orbitals had different energy right
and then we fill electrons in this
orbital spatial energy
similarly molecular orbital things
Theory talks about a concept where use
molecules and molecules and then
molecules will have orbitals and
orbitals in this molecule this molecule
orbitals will have different energies
and when you fill electrons in these
molecular orbitals it will based on the
similar principle of bowel principles
and to scale of things later so the
shift here is instead of of considering
molecules as two different atoms it
considered molecules as molecules right
so you see it says that the electrons in
the molecules are present in various
molecular orbital because I'm talking
about molecule as one entity and I have
orbitals in the molecules that is called
molecule orbitals and electrons are
present in that right so atomic orbitals
of comparable energies and symmetry
combined to form molecular orbitals so
how you get molecular orbitals when are
atomic orbitals of comparable energies
and symmetry they combined to form
molecular orbitals so the way they have
done here is so this is my s orbital s
atomic orbital these are my 2 s atomic
orbitals these are my atomic orbitals it
forms molecular so this is also my
molecular the one on the right is also
more liquid or this is a common in this
case if you see 2's atomic orbitals
combine to form molecule
to my cottage here also the law of
conservation of orbital will to hold
true if two atomic orbitals a combining
uniform to moloch robbery
bonding this guy's bonding and there
will be antibody right here oh who says
it is a head-on collision head on head
on overlap it is a sigma s already Sigma
s the Sigma H star antibonding ama tree
similarly you have a hero say for P also
P also you have your head on bonding
right this atomic orbital it forms one
bonding and one antibody hungry in the
morning
Meleager already correct so it's saying
that atomic orbitals will come the rebel
energy form a comparable energy and
symmetry forms molecular orbital and
then once you have molecule orbital use
you who are trying to fill electrons in
that molecular orbitals as if you are
filling electrons now I'll explain those
things we will take for example this
understand then talks about molecular
orbitals it use the orbitals in the
molecule as molecular orbital itself
right and says that we have one bonding
molecular orbital N and I'm D bonding
bonding has higher energy and D bonding
has lower energy sorry bonding has no
other energies stable and Demond against
higher energy is pretty unstable and the
you see the distribution also there is a
nodal plane here actually there is no
here there is no electron this is also
known there is no electrons here it also
it is known here to explain this more
when we discuss this in detail also know
dad's atomic orbital is more eccentric
if you see these guys has one electrons
but let me talk about molecular orbital
is poly same thing in this case they are
two electrons see two degrees so in
atomic orbitals there one
yes more eccentric but if you see
talking about this atomic orbital
molecular orbital they have their
Pauline centering in this case two
degrees here also it is something on top
of this so the nucleus is both if you
see this case there are two atoms when
they combine they can VSS overlap right
so when there is SS overlap it will form
empty bonding and bonding s orbital see
two atoms combine that is a fact
experimental fact now the structure the
behavior all this thing has to be
explained we explain this there so many
theories this is a different theory
altogether don't get confused whether
the last three which we have learnt well
as more theory is a total different
theory altogether which talks about
molecular orbital and don't mix things
because they are different approaches to
explain the national phenomena of
chemical bonding so this approach is
totally different from the valence bond
approach this approach says that they
are to see atom looks like this that is
pretty clear experimentally they have
seen this now when an atom combines so
valence bond Theory talks about orbital
overlap but molecular orbital does not
talk about all those things say is that
S & S orbital atomic orbital will
combine to form molecular orbital then
you have P and P atomic orbital will
combine to form molecular orbital
similarly atomic orbital combined to
form molecular orbital and not atomic
orbital is more eccentric and molecular
orbital is polishing it correct let's
understand this molecular orbital theory
in detail as I told the law of
conservation of orbital is followed here
also the number of molecular orbital
form is equal to the number of
finding it example if you see these are
two atomic orbital right two atomic
orbitals are combining so it gives one
bonding molecular orbital and one nt1 ND
morning Molly gravity sorry these are
all right Omega a dresser - 1 s 1 s 2
atomic orbital combined and it gave to
way it gave to actually you can think of
this pathway or sorry
he says class this is - and why it is
like this because because these orbitals
as we have learned are nothing but Soren
jet equation wave form
okay so we'll explain why it is in the
next slide as understand that in this
case the law of conservation of orbital
is formed when two atomic already will
combine to molecule orbital or form one
is known as morning the other is gone
antibonding sorry the bonding will have
lower energy and they are stable 90
running will have higher energy so are
unstable in this case also ABC this is p
orbital this p orbital this combines
they form Sigma T Sigma P and Sigma V
Star this is antibonding molecular
orbital and this is morning one of you
are here now CPC PNP combined form pi PI
molecular orbital so this guy is my
bonding molecular orbital and this is my
auntie foil right and this they have
known say this is my node since my nodal
plane boards where there is no electron
here since the nodes actually now the
question is why it forms bonding and
antibonding molecule orbitals so why two
guys that is pretty simple
see this this orbital is nothing but my
wave function
and coming up in something but my
wavefunction so when I am saying my
wavefunction one and I'm saying
wavefunction - I can either plus it or I
can - it because this is destructive and
constructive constructive interference
correct so one output will be you add
these to be a function and the other
will be you subscribe this rule right so
if there this is my wave function if you
subtract this you get nt morning is
subtraction when you add these you get
bondola or in the sandwich see atomic
orbital is nothing but my wave function
right so these is this can be obtained
by the solution prompts oranger equation
so it can either add or subtract so when
you add the waves it becomes something
like this when you do a subtraction
becomes something like this here also if
you see when you add these two when you
add these two when you add these two
actually it becomes something like this
on addition on subtraction it will be
something like this you just saw a
subtraction you flip this see for
addition you just added so this will
become bigger you become like this
so traction you flip this and then add
so you see it becomes something like
this so really here also for addition in
something like this will be added
subtraction will be something like this
this dark and light color is just so
that it got flipped the subtracting this
is Plus this is minus of trotting it
will flip it and then add thanks you can
flip it in man
you become something like this the node
here he also there is a node is a node
it's of antibody antibonding has higher
energy and they are unstable and these
are bonding this is also bonding
molecule other bonding mo
this is anti-bonding em right correct
this is a bonding this is auntie morning
this is how it looks like actually thank
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