Formulate Bohr’s quantum postulates.

The first postulate: there are special states of the atom in which it does not emit energy, although charged particles move with acceleration. These states are called stationary states. The second postulate: any radiation of an atom is associated with a transition from one stationary state to another and always consists of purely harmonic waves. The frequency of these waves does not depend directly on the motion of the electron in the atom, but is determined by the so-called frequency conditions.