Nuclear binding energy is the minimum energy that is required to disassemble the nucleus of an atom into its constituent protons and neutrons, known collectively as nucleons. The binding energy is always a positive number, as the nucleus must gain energy for the nucleons to move apart from each other. Nucleons attracted to each other by the strong nuclear force. These nuclear binding energies and forces are on the order of one million times greater than the electron binding energies of light atoms like hydrogen.