Bohr model

A combination of the Rutherford model of the atom with the quantum theory, based on the following four postulates: 1. An electron in an atom moves in a circular orbit about the nucleus under the influence of the electrostatic attraction between the electron and the nucleus. 2. An electron can move only in an orbit for which its orbital angular momentum is an integral multiple of h/2π, where h is Planck's constant. 3. An electron moving in such an orbit does not radiate electromagnetic energy and so its total energy E remains constant. 4. Electromagnetic radiation is emitted if an electron makes a transition from an orbit of energy E _i to one of lower energy E _f , and the frequency of the emitted radiation is v=(E _i -E _f )/ h.