1. The problem statement, all variables and given/known data What exactly is binding energy? why is this energy RELEASED during fission / fusion 2. Relevant equations 3. The attempt at a solution when two light nucleons fuse they combine to form a heavier nucleon whose mass is less than the sum of the two seperate nucleons. This lost mass goes into making the binding energy. It seems that the binding energy is the energy needed to hold the nucleus together. WHY IS THIS ENERGY RELEASED?