In the case of formation of a nucleus the evolution of energy to the binding energy of the nucleus takes place due to disappearance of a fraction of the total mass, If the quantity of mass disappearing is , then the binding energy is

From the above discussion, it is clear that the mass of the nucleuses must be less than the sum of the masses of the constituent neutrons and protons. We can then write.

Where is the mass of the atom of mass number A and atomic number Z. Hence, the binding energy of the nucleus is

Where number of neutrons,