Why is so much energy produced when an atom is split or fused?
What is meant here by “so much energy” — much relative to what? The answer is relative to the mass of the fuel used. (If we burn enough fuel we can make as much electricity in a coal-fired power plant as in a nuclear one.) In any process the energy produced is determined by how much mass is converted to energy, following the rule E=mc2. So what we are really interested in here is the fraction of the mass that is released in the process. The short answer to your question is that the energy release in nuclear fission or fusion is a larger fraction of the mass of the fuel than in chemical processes because the binding forces (and hence the binding energies) between the protons and neutrons in nuclei are much larger than those for atoms in a molecule or solid. To understand this first let’s look at a coal-burning power plant (that is for combustion or for any other energy-releasing chemical reaction). The usual rule taught in chemistry is that mass is conserved. The precise version of thi
