Bohr model of hydrogen - Structure of Atom Video Lecture - Class 11

hello friends this video on structure of
atom part 22 is brought to you by exam
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no more fear from exam before watching
this video please make sure that you
have watched part 1 to part 21 so let's
see the Bohr model in 1993 the
postulates of the Edward the Bohr model
conveyed that time so the final going to
the Bohr model was the electron of the
hydrogen atom can move around the knee
plus in the circular path fixed radius
and they all have fixed energies right
they are called orbits and these orbits
are arranged comes some quickly around
the nucleus like this the energy of the
electron in the orbit does not change
with time the energy if example you have
a electron here it log is the same if it
is in this orbit electron will move from
lower to higher lower station a shade to
a higher stationary shape when required
amount of energies absorb or ramble in
this case if it emits some energy it
will go to the lower state if it absorbs
it absorbs it will go to the higher
state and the Delta s is nothing but
this rh / constant by 1 - an initial
square - any final score and the
frequency of radiation absorbed or
emitted and transition occurs between
the stationary States is nothing but you
see Delta is also I can write as H mu so
view is nothing but Delta e by H so we
got frequency as Delta Y by H correct
the angular momentum of electron in a
given stationary shape indeed space to
this equation MV R is nothing but n H by
2 pi where n can have any values 1 2 3 4
that is the formula for the annual
moment of electing our momentum of
electron in a particular orbit and
please what once again I am getting the
orbit concept is strong it does not
exist in real this was just a concept by
board these still study this because it
makes us easy to understand that
because the quantum model is little
complex to understand but still this
model is incorrect the stationary states
of electrons are number n is equal to
one two three and they are called
principle quantum number there is the
only quantum number required at that
point of time in Bohr model to to
uniquely define an orbit and the radius
four he also get the formula to find the
radius of the Ilia orbit that is R is n
but n square a not and in orders 529 P
comma right so five 52.9 actually so if
you see if you put n is going to 1 you
get the station radius of the first
stationary say does 52.9 if you put n
equal to 1 and please know this
stationary state does not mean the
electron is stationary I'll tell you
electron can never be stationary it is
not possible to have a stationary
electron it can never be stationary
correct and the most important property
with the electron is the energy and he
also gave the formula to give them
energy with of it's stationary state
that is e is nothing but minus 1 by r h
1 by r square that's the energy of a
electron in a particular orbit so you
get a lot of formulas to find the
momentum a DI energy but still the orbit
considers wrong and bora-bora theory can
also be applied to ions containing one
electron please note this board theory
was generally for one electron so
hydrogen is fine or any ions with ample
helium i lithium plus 2 beta alumina
which is only one electron both carry
work we did into that because the very
simplified story on or simplified model
of the actual quantum model and that's
why we put cross dressing boom
because if you understand the board
model it's easy to understand the condom
model it's very base basic form a
quantum models and it is also possible
to calculate the velocities of electron
moving in this orbits right and the
magnitude of velocity increase with the
increase in positive charge the new flag
and D an increase of principal quanta
so if you see what I am saying is if my
electron or the new the charge is more
on the atom if you have more protons
right more protons more protons more
protons the velocity will be more if you
increase the proton if you keep the
protein content if you go from one orbit
to a higher orbit if you go to higher
orbits the velocity will be less because
it decrease with increase in clinical
quantum number so if we are not able to
understand this you can ignore this now
because we'll study the actual quantum
model also where we will tell you how to
find the velocity impact on the on
bridges there we have the term claw
orbitals not down but here where is in
term orbit orbit is something which
doesn't exist now the question is in
Bohr model of hydrogen energy is
negative Y so negative signs means the
energy is lower than the energy of free
electron at rest
see first thing electron will never be
at last right so this is nothing but of
electron which is not in effect of any
charge I can say that is the energy of
electron they are talking about that is
infinitely away from you clay so what
they are saying is if I have electron
somewhere in finite distance here and if
I assume this guy has zero energy the
moment I take it here it will lose some
energy and you go - it will go here lose
further more energy so let's a believe
it is fine in the minus five year
becomes minus six here becomes minus
seven
it keeps losing energy why because it
lose energy and it gives you the photon
light that's how you have seen if the
electrons jump from higher orbit into
lower orbit it loses energy and it emits
a photon so we can't assume the energy
to be zero here right so what we are
doing is we're assuming the energy is
zero at the infinite distance please no
be assuming it is 0 it is not 0 we are
assuming because we had to give some
number so we are assuming it is zero
just for the convenience of our
calculations we are giving it zero here
then we are telling that if you take
this electron to this place it lose some
energy because it will be now in it will
be slave of this photon you can say
because it will be controlled else
Photon so it lose some energy it goes
further down the lever it loose for the
more energy and keeps losing energy till
it's reach this n is equal to 1 the
least energy state and that's why the
energy is negative because at this point
it is 0 and if it is losing energy it
has to be negative it can be positive
and that's why it is negative right and
that's what they are saying when was
freed from the nucleus influence it is
taken to be 0 and when the electron is
attracted by the nucleus in its present
orbit n the energy is emitted and
lowered so same thing so you you just
keep going to the town level you keep
losing energy and the max you can do is
n is equal to 1 it you cannot go beyond
this and the board didn't have any
explanation for this we will have the
explanation for this in the quantum
model why the electron can't go and jump
into this nucleus this understand that
why the energy is negative is because of
the infinite distance we are assuming
there is is zero when it comes to comes
near the neutron comes different orbits
it keeps losing energy and it goes to
the lowest possible energy level and
thus ceases lost energy it is negative
so if you see each of this picture lines
if you can I'd told the energy is
quantized
the spectral line is because of a
movement of electron from one orbit to
another each of this spectral line C D
Phi is one movement and also if you have
large number of hydrogen atoms and
different possible transition can be
also and that's why you'll see lot of
lines but you'll have six lines only
because these lines is not possible as
for this I adult is concerned and the
brightness of this will also depend the
number of photons do not depend on the
frequency it will depend on the number
of photons of same wavelength so they
told earlier according to board the
energy is absorbed energy is absorbed in
electron moves from orbit of smaller
quantum number to hire conduction sample
from here it moves to here so in this
case energy is absorbed and if it is
going from higher to lower energies in
red if you see energy is emitted okay LC
energy is M so on here energy is emitted
and this energy gap is nothing but e
final minus V initial and I know that
every orbit has energy defined both has
defined that also if you bother me
whatever the energy orbital ha yes
defined that we can find in Tahiti
correct and that gives the line spectrum
because you can have only fixed set of
Delta e and fixed center of it I will be
corresponding to a fixed set of lambda
and fix it of lambda will means that
means we have fixed set of spectral
sorry for stability of atom or gave a
explanation that in a particular orbit
energy is conserved if you take electron
anywhere in this orbit it allows same
energy and since he is sharing that the
the electron is moving in the same orbit
it is not losing energy say the energy
is not lost it is moving with a
particular velocity there is no friction
there so it is keeps moving in the same
orbit the concept we told was there is
energy is same for any
in particular or only when the electron
jumps from a higher orbit to lower orbit
it emits energy or when it jumps from
lower to higher energy it needs some
energy so that energy change required to
event is a jump of electron from orbit a
to orbit B but if it is whatever orbit
the energy is constant and that's why I
saying that it keeps moving but still I
do not find answer to be very convincing
the quantum modelling is a better
explanation to this to understand this
when we discuss the quantum model so
Bohr model has lot of limitations
see your model has a lot of limitations
the first is it was mainly for hydration
the second was it could not explain the
specter of multi-electron atoms it could
explain the spectra of hydrogen atoms
very well but it could not explain the
spectrum multi-regional atom and also he
observed he assumed electrons as
discharged particle so the wave
character was ignored as I told right
the duality principle of electrons will
pass at that time but he ignored that
completely and he considered electrons
only as particle and it was not able to
explain the ability of atoms to form
molecules by chemical bonds and it
contradicts with the Heisenberg
uncertainty principle is a very strong
principle at that point of time and the
g---men effect that is there when we see
the deviation in the spectral line due
to magnetic field that could not be
explained also the stark effect that is
nothing but change spectral line three
linked electric field that also could
not be extended talk about diamond stark
effect later also and the Solingen
equation came out after the Bohr model
and that allowed that gave a better
explanation of distribution of electron
in the space and gave equation for
different orbitals so at least our
linear equation we have a better
explanation of the atom than pores so
Bohr become an obsolete model and
syringes quantum model becomes the power
model thank you visit exam viacom to
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