Binding Energy Curve
The mass of a nucleus is less than the sum of it constituent protons and neutrons. If we took the same number of protons and neutrons as in the nucleus we were trying to recreate, we would find the total mass of the individual protons and neutrons is greater than when they are arranged as a nucleus. The difference is known as the mass defect. The binding energy is also the amount of energy required to break the nucleus into protons and neutrons again; the larger the binding energy, the more difficult that would be. Figure. 1. Shows the binding energy of all the elements, against their atomic number.
Starting from Hydrogen, as we increase the atomic number, the binding energy increases. So Helium has a greater binding energy per nucleon than Hydrogen while Lithium has a greater binding energy than Helium, and Berilium has a greater binding energy than Lithium, and so on. This trend continues, until we reach iron. It begins to decrease slowly.
