Why is more energy released in a fusion reaction than in a fission reaction?
william1941 Teacher Community / Jr. College Expert $(document).ready(function() { $(‘a.toggle_expert_titles’).click(function() { $(‘#show_expert_titles’).toggle(); return false; }); }); Best answer as selected by question asker. In both fission as well as fusion reactions the energy released is proportional to the decrease in the mass of the products of the reaction compared to the mass of the elements the reaction starts with. In the case of fission, the energy released is high for atoms which have a large mass initially. The energy released for a reaction involving uranium or plutonium is around 200 MeV. This is large, but if it is divided by the number of nucleons it is around 1 MeV per nucleon. For the fusion of 4 Hydrogen nuclei into a helium nucleus around 27 MeV, of energy is released, this if divided by the number of nucleons is about 7 MeV per nucleon. Therfore the energy released per nucleon is more in the case of fusion than fission. Fusion reactions yield a positive energy
