Immediately after the existence of neutron was experimentally confirmed physicst proposed the proton– meutron hypothesis of atomic nucleus. Protons and neutrons taken together are referred to as nucleons.
According to this hypothesis a nucleus \(^A_Z X\) is made up of z protons and (A-Z) neutrons
The theoretical and experimental values of (1) nuclear spin and (2) nuclear magnetic moment are in agreement with theortical calculated and experimental values. Also the uncertaintity principle is not violated. The hypothesis also easily explains existance of isotopes; isobars etc. It is the presently accepted model of atomic nucleus.
