So I was wondering why do nucleons need to remove mass to form a nucleus. Is it because it lowers the energy of the nucleus making it more stable or something completely different. I understand that it is the energy input to break the nucleus into its components, however, why do nuclear reaction release so much energy. II also understand that in fission and fusion reactions the binding energy per nucleons increase after the reaction, but is that all? I know I sound slightly confused but just want clarification.