What are fission and fusion reactions?
As we saw earlier, energy will be released in a nuclear reaction if the total binding energy of the reactants is less than the binding energy of the products. Careful measurements of the binding energy of nuclei show that the binding energy per constituent particle (proton or neutron, collectively called nucleon) of a nucleus increases for light nuclei as their weight increases, where as for heavy nuclei it decreases as their weight increases (see Figure 4). For example, the binding energy per particle in deuterium (1 proton, 1 neutron) is less than in helium (2 protons, 2 neutrons). However as the atom becomes heavier (exceeding about 26 protons in its nucleus, corresponding to the iron nucleus), the trend reverses. Hence, the binding energy per nucleon in uranium (92 protons, 143 neutrons) is less than in iron (26 protons, 30 neutrons). There are therefore two possible kinds of nuclear reactions in which energy may be released. If a heavy nucleus splits into two roughly equal sized n
