Publish On: 2019-05-24


Total Post: 504

Question: Describe the Bohr model of hydrogen atom

Reply On: 2013-10-09

lala singh

Total Post: 22

ANS: Describe the Bohr model of hydrogen atom

In view of the limitations of Rutherford atom model, Niels Bohr came to the conclusion that classical mechanics and electromagnetism could not be applied to the processes on the atomic scale. Bohr cleverly combined classical ideas and early quantum concepts (given by Planck) to give what is known as Bohr model of hydrogen atom. Following are the three postulates of this model:

1. Every atom consists of a central core called nucleus. In which entire positive charge and almost entire mass of the atom are concentrated. A suitable number of electrons (having as much negative charge as the positive charge on the nucleus) revolve around the nucleus in circular orbits. The centripetal force required for revolution is provided by the electrostatic force of attraction between the electron and the nucleus.

This postulate stresses that an electron in an atom can revolve in certain stable orbits only without the emission of radiant energy. Thus, each atomic exist only in certain definite stable states with definite total energy. These are called stationary states of the atom.

2. Bohr’s second postulate defines these stable orbits.

According to Bohr, electron can revolve only in certain discrete non radiating orbits, called stationary orbits, for which total angular momentum of revolving electron is an integral multiple of h/2∏, where h is Planck’s constant.

Thus the angular momentum of the orbiting electron is quantized.

3. The emission/absorption of energy occurs only when an electron jumps from one of its specified non-radiating orbit to another. The difference in the total energy of electron in the two permitted orbits is absorbed when the electron jumps from inner to the outer orbit, and emitted when electron jumps from outer to the inner orbit.


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