As you have studied in section 3.3, Rutherford’s model could not solve the problem of atomic mass. The existence of the neutron thus accounted for the mass of the atom. Another drawback which Rutherford’s model suffered was that it could not explain the stability of the atom. According to the electromagnetic theory of radiation, a moving charged particle, such as the electron which is constantly accelerating because of change in directions of motion, should emit radiation. The energy of the radiation would come from the motion of the electron. Thus, the electron would emit radiation and follow a spiral path as shown in Fig.3.6.

The energy of the electron would keep on decreasing (as the electron would keep on emitting radiation) till the electron finally falls into the nucleus. But actually it does not happen. The electron does not collapse into the nucleus. Thus, Rutherford’s model needed the improvements which were later on suggested by Bohr. Bohr’s model now will be discussed in the next section.