Mass deficiency describes the fact that the nuclei made up of protons and neutrons have a smaller rest massThe mass of a particle at rest. According to the theory of r... than the sum of the rest masses of the protons and neutrons forming the nucleusPositively charged nucleus of an atom. Its diameter amounts .... The mass difference is equal to the released binding energyThe energy required to separate particles which are bound by.... For the alpha particlePositively charged particle emitted by various radioactive m... with a mass of 4.00151 atomic mass units, the structure of two protons (1.00728 atomic mass units each) and two neutrons (1.00866 atomic mass units each), a mass defect of 0.03037 atomic mass units results. This corresponds to an energyAbility to do work or diffuse heat. The unit of energy is th... (binding energyThe energy required to separate particles which are bound by...) of about 28 MeVMegaelectron volt, 1,000,000 eV..