text: The term  or  is known as the Coulomb or electrostatic term.
  The basis for this term is the electrostatic repulsion between protons. To a very rough approximation, the nucleus can be considered a sphere of uniform charge density. The potential energy of such a charge distribution can be shown to be
  where Q is the total charge, and R is the radius of the sphere. The value of  can be approximately calculated by using this equation to calculate the potential energy, using an empirical nuclear radius of  and Q = Ze. However, because electrostatic repulsion will only exist for more than one proton,  becomes :
  where now the electrostatic Coulomb constant  is
  Using the fine-structure constant, we can rewrite the value of  as
  where  is the fine-structure constant, and  is the radius of a nucleus, giving  to be approximately 1.25 femtometers.  is the proton reduced Compton wavelength, and  is the proton mass. This gives  an approximate theoretical value of 0.691 MeV, not far from the measured value.