Cracking the SAT Physics Subject Test

What happened to this missing mass? It was converted to energy when the deuteron
was formed. It also represents the amount of energy needed to break the deuteron
into a separate proton and neutron. Since this tells us how strongly the nucleus is
bound, it is called the binding energy of the nucleus.

The conversion between mass and energy is given by Einstein’s mass–

energy equivalence equation, E = mc^2 (where c is the speed of light);

the binding energy, EB, is equal to the mass defect, ∆m.

EB = (∆m)c^2

Using E = mc^2 , the energy equivalent of 1 atomic mass unit is about 931

MeV.

In terms of electronvolts, then, the binding energy of the deuteron is

Since the deuteron contains 2 nucleons, the binding energy per nucleon is

This is the lowest value of all nuclides. The highest, 8.8 MeV/nucleon, is for an

isotope of nickel,^62 Ni. Typically, when nuclei smaller than nickel are fused to form
a single nucleus, the binding energy per nucleon increases, which tells us that
energy is released in the process. On the other hand, when nuclei larger than nickel
are split, binding energy per nucleon again increases, releasing energy.