Bohr’s Atomic Model

In 1913, Niels Bohr (1885-1962) proposed another model of the atom where electrons move around the nucleus in circular paths. Bohr’s atomic model is built upon a set of postulates.

1. The electrons move in a definite circular paths around the nucleus. He called these circular paths as orbits and postulated that as long as the electron is in a given orbit its energy does not change (or energy remains fixed). These orbits were referred to as stationary orbits or stationary states or non-radiating orbits.

2. The electron can change its orbit by absorbing or releasing energy. An electron at a lower (initial) state of energy, E_i can go to a (final) higher state of energy, E_f by absorbing a single photon of energy, E.

E = hv = E_f – E_i

Similarly, when electron changes its orbit from a higher initial state of energy E_i to a lower final state of energy E_f, a single photon of energy hν is released.

3. The angular momentum of an electron of mass m_e moving in a circular orbit of radius r and velocity v is an integral multiple of h/2π.