Question

Hans Bethe (prominent nuclear physicist) once remarked that he considered everything before 1932 “the prehistory of nuclear physics, and from 1932 the history of nuclear physics.” The difference he said was the discovery of the neutron . Explain why?

Answer 1

Before the discovery of neutron it was believed that nucleus s composed of protons and electrons. But there were many contradictions with this concept like quantum mechanics suggested that electrons simply could not be in the nucleus.  As suggested by uncertainty principle that no particle can be containesd in a stationary state in space which is smaller than its Compton wavelength h/mc, therefore the nucleus being much too small to contain electrons It was then also found that the statistics of nuclei and spin of nuclei contradicted the idea of the constitution in terms of electrons and protons. In this period physicsts were at complete loss and it would had been impossible to construct any logical theory on nuclear structure if Neutron would not had been discovered in 1932.