Concept of Binding Energy

Consider the following reaction

• Mass of the product nucleus is less than the sum of the masses of reactant nuclei by an
  equivalent of 2.23 MeV.
• Another way of looking at this is that a proton and neutron, the constituents of deuterium
  nuclei, bind themselves by releasing binding energy of 2.23 MeV.
• This implies that we need to supply 2.23 MeV to break deuterium nuclei into its constituents.
• In general, when particles bind themselves they release energy.