1. The problem statement, all variables and given/known data We just started binding energy things in class starting off with e=mc^2 and well in my notes it says. "If weakly bound nuclei transform into more strongly bound nuclei, the total mass can be reduced and the mass energy of the final state is lower than the mass energy of the initial state 2. Relevant equations 3. The attempt at a solution Heres how I understand that sentance. In the initial state the nucleons inside the weakly bound nuclei are bound weakly to each other, this means that there is low binding energy between them. In the final state the nucleons inside the strongly bound nuclei and strongly bound to each other, meaning that there is a high binding energy between them. What I don't understand is how the "total mass can be reduced". Also it goes on to say "and the mass energy of the final state is lower than the mass energy of the initial state" If the binding energy is higher in the final state, surely the energy in the final state is higher? I mean unless the mass change overides that or has a greater impact than the energy change. Thats how I see it.