The postulates of the Bohr model of the hydrogen atom can be stated as follows:

(I) The electron can exist only in discrete states each with a definite energy.
(II) The electron can exist only in certain circular orbits.
(III) The angular momentum of the electron is nh/2( where n is any positive integer.
(IV) Radiation is emitted by the atom only when an electron makes a transition from a state of higher energy to one of lower energy.

(a) State whether each of these postulates is currently considered to be correct, according to the wave mechanical description of the hydrogen atom.
(b) Give the wave mechanical description that has replaced one of the postulates now considered to be incorrect.

I,III,IV are valid assumptions in the wave mechanical model II has been replaced by the assumption that the electrons are not found in a particular orbit but is distributed throughout the atom hence we can only talk about the probability of finding the electron within a given volume element. Psi^2dxdydz is the probability of finding the electron in a given volume element.

Explanation:

Bohr assumed that electrons are found in specified orbits. This idea is incongruent with the Heisenberg uncertainty principle. By following the deBroglie idea of matter-waves, Erwin Schrödinger arrived at the Schrödinger wave equation which describes the energy of an electron in the hydrogen atom from a wave mechanical perspective.