Bohr's Model of the Hydrogen Atom Video Lecture - Physics Class 12 - NEET

professor Dave here, let's talk about
the Bohr model of the atom
once Einstein extendedplanks idea of energy quantization to
electromagnetic radiation other
physicists made some similar strides.
Niels Bohr was dealing with some
problems that were arising with the
structure of the atom. if an atom has
positively charged protons and
negatively charged electrons, why are atoms
stable? why don't the electrons just
collide with the nucleus? and what were
these emission spectra that we can see?
what is it about different elements that
makes them emit light of different
colors? bohr answered these questions with
his model of the hydrogen atom. he
extended the idea of energy quantization
and said that the potential energy of
the electron in a hydrogen atom is also
quantized. this means that an electron
can't have any imaginable energy but can
only inhabit certain energy levels that
are at fixed distances from the nucleus
each type of atom has its energy levels
at different values due to its unique
number of protons in the nucleus and an
electron will transition from one energy
level to another when a photon of a very
specific energy is either absorbed or
emitted by the electron. the energy of the
photon will correspond to the difference
between the two energy levels so if the
electron in a hydrogen atom goes from
the n=3 to the n=2 energy
level, a photon will be emitted that is
equivalent to that specific energy gap.
another transition has a different
energy gap associated with it and
therefore generate a photon of that
particular energy. and to go from lower
to higher energy levels an electron
must absorb a photon of that particular
energy. for a hydrogen atom the energy
levels depend on the Rydberg constant
and are given by the following equation
but we typically just measure the change
in energy of an electron during a
transition so we can modify this
equation to include the change in the
energy level. n final is where the
electron ends and n initial is where it
begins. using this equation we can
predict the wavelength of photon
associated with any
possible transition for the hydrogen
atom. take this transition for example
from 4 to 2. plug in where the electron
starts and where it ends and we get the
change in energy of the electron which
equals the energy of the photon
from energy we can get frequency
and from frequency we can get wavelength
we group the transitions according to
the energy level they land on. all the
ones that end on n=1 are called
the lyman series. the ones that end at
n=2 are the balmer series, and
so forth
notice that the energy level gaps
decrease as n increases and n equals
infinity is actually a finite distance
from the nucleus. if an electron goes
beyond that it is considered to have
been ejected from the atom. the Balmer
series happens to contain transitions
that generate photons of visible light
these are the ones found on the hydrogen
emission spectrum. these lines correspond
to the electrons transitions that end at
n=2 and the resulting photon
that transition emits which just
happens to fall in the visible spectrum
as we said these energies are unique to
hydrogen, every element will have its own
emission spectrum because every element
has a unique nucleus and therefore
differently spaced energy levels. in this
way an element's emission spectrum is
sort of like a fingerprint unique to
that element. this is how we can know the
composition of objects in space, by
analyzing the light we see. let's check comprehension
comprehension thanks for watching guys
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