Bohr proposed the atomic model in 1912 AD. It was called Bohr’s atomic model. It’s main postulates are as follow—

(i) The electrons in an atom revolve around the nucleus in a definite circular path these paths are called electronic orbit. It is known as the energy level.

(ii) The electronic orbit is free from energy.

(iii) Electron energy levels are denoted by K, L, M....... or 1, 2, 3..........

(iv) An electron can lose or gain only a certain and required energy.