So, how big are the nuclear forces?
A measure of the strength of the nuclear forces is given by the ‘nuclear binding energy’, which is the amount of energy that would be needed to break the nucleus up into its constituent particles. This can be calculated from what is called the ‘mass defect’ of the nucleus. (The rest mass of the nucleus is always slightly less than the sum of the masses of its constituent nucleons.) The loss of mass is accounted for by the concept of mass-energy equivalence — part of Einstein’s Theory of Relativity. Thus, the mass defect corresponds to the energy which would be liberated if a nucleus were formed from protons and neutrons and which would have to be supplied to break the nucleus up into these particles. The quantity of binding energy is given by multiplying the mass defect by the square of the speed of light, which is an enormous figure! Models of the Nucleus A detailed description of nuclear structure is beyond the scope of this entry. Suffice it to say that there are four major models t
