NUCLEAR BINDING ENERGY

Mass defect

The sum of the masses of the constituent nuclei is always more than the actual mass of the resulting nucleus. The difference between the masses of the constituent nucleons and the actual mass of the nucleus is called the mass defect. Let M be the mass of the nucleus having the mass number A and atomic number Z.
Mass defect,∆m= [Zmp+(A-Z)mn]-M
Where mp is the mass of the proton and mn is the mass of the neutron

Binding energy

When protons and neutrons combine to form a nucleus, the mass that disappear (mass defect) is converted into equivalent amount of energy. This energy is called binding energy of the nucleus.
Binding energy =mass defect x c2=∆mxc2=[Zmp+(A-Z)mn-M]c2
The binding energy determines the stability of the nucleus. If the binding energy is large the nucleus is stable and vice versa. The binding energy must be supplied to the nucleus to split into completely into its constituent nucleons.