Introduction to Bohr’s Atomic Model

Quantization of energy

All the elements are made up of small particles known as an atom. An atom is composed of sub atomic particles viz. proton, electron and neutron. Various scientists proposed different models of the atom at different times which led to the discovery of the structure of the atom.

Bohr’s atomic model:

Niels Bohr in 1911 proposed a model of hydrogen atom based  on the Planck’s quantum theory. He assumed the atomic theory proposed by Rutherford and tried to overcome the defects of the theory. The postulates he proposed are:

1. Atom consists of a positively charged nucleus with negatively charged electrons revolving around it in different orbits.
2. Only those orbits are possible for which the angular momentum of electron is integral multiple of h/2π i.e., mvr = nh/2π where where n= 1, 2, 3… .
3. Electrons do not radiate energy as long as it remains in its own orbit. Electrons jump from higher orbit to lower orbit radiating energy in the form of photon and may jump from lower orbit to higher level absorbing energy. The  frequency of emitted photon when electrons jump from energy state E1 to energy state E2 is given by: $$F = \frac{e_2 – e_1}{h}$$
4. The energy of an electron always remains constant when the electron revolves in an orbit.

From Bohr’s atomic theory, radius and velocity of the electron can be determined.  It also explains the stability of the atom and hydrogen spectra.

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