Read the passage below and answer the question.

Atom contains dense mass at its center, called nucleus. Nucleus is positively charged. Nucleus is made up of neutrons and protons. Therefore, it may be expected that the mass of the nucleus is equal to its individual protons and neutrons. However, the nuclear mass M is found to be always less than this. 

If a certain number of neutrons and protons are brought together to form a nucleus, then a fixed amount of energy is associated with it. What is it called?

Binding Energy

Definiton.