Question

Write three postulates of Bohr. Mention two limitations of Bohr model.

Answer 1

Three postulates of Bohr are

1. An atom has a number of stable orbits in which an electron can reside without the emission of radiant energy. Each orbit corresponds, to a certain energy level.

2. An electron may jump spontaneously from one orbit (energy level $E_1$) to the other orbit (energy level $E_2$) ($E_2>E_1$); then the energy change $A_E$ in the electron jump is given by Planck’s equation.

3.The motion of an electron in a circular orbit is restricted in such a manner that its angular momentum is an integral multiple of $h/2\pi$.

Limitations of Bohr model :

1. It is in violation of the Heisenberg Uncertainty Principle. The Bohr Model considers electrons to have both a known radius and orbit, which is impossible according to Heisenberg.

2. The Bohr Model is very limited in terms of size. Poor spectral predictions are obtained when larger atoms are in question.