In 1913, Niels Bohr put forward his theory regarding the structure of an atom. He retained the main features of Rutherford’s nuclear model and proposed some modifications. The proposed model is known as Bohr’s model. Its salient features are as follows.

1. The nucleus of an atom is situated at its centre

2. The electrons in an atom move around the nucleus in definite circular orbits known as energy levels or shells.

3. Each energy level is associated with a fixed amount of energy.


4. The energy levels starting from the one closest to the nucleus are numbered as 1, 2, 3, 4, etc, or designated as K, L, M, N, etc.

5. An electron neither loses nor gains energy if it keeps moving in one of these energy levels.

6. An electron can move from one energy level to another. If it jumps from a higher energy level to a lower energy level, it emits energy. If it jumps from a lower energy level to a higher energy level, it absorbs energy.