In 1913 Prof. Niels Bohr proposed a quantum model of the atom in order to explain the stability of the atom. Assumptions made by Bohr to explain his atomic model.
1. Bohr's First Assumption: Electrons rotate in the non-radiating circular orbit around the nucleus in the stationary orbit. The centripetal force keeps all the electrons in the circular orbit which is maintained by the Coulomb force. i.e. Centripetal force is equal to Coulomb force.
Let's say an electron (-e) of mass m is moving with a velocity v and in radius r around the nucleus of charge (+Ze). So the Coulomb force of attraction can be written as:
Coulomb’s Law is equivalent to the centrifugal force, so that we can write that: F= 1/4πε ((-e)(+Ze))/r^2 = (mv^2)/r
2. Bohr's 2nd Assumption: An electron can revolve only in those orbits in which the total angular momentum of the electron is equal to an integral multiple of h/2Ï€, where h is the Planck's Constant. These orbits are called stable orbits.
3. Bohr's 3rd Assumption: No energy is radiated by the atom so long as the electron continues to move in stationary orbits. The emission or absorption of energy takes place only when an electron jumps from one stable orbit to another stable orbit.
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Check more: Matter in The Universe
