Binding energy and stablity of atom

Binding energy is the energy that is lost when a nucleus is created from protons and neutrons. If you added up the total mass of the nucleons (protons and neutrons) that compose an atom, you would notice that this sum is less than the actual mass of the atom. This missing mass, called the mass defect, is a measure of the atom's binding energy. It is released during the formation of a nucleus from the composing nucleons. This energy would have to be put back into the nucleus in order to decompose it into its individual nucleons. The greater the binding energy per nucleon in the atom, the greater the atom's stability....excerpts from libraryquest.com