Mass defect

Mass defect is the difference between a bound system’s mass and the sum of the masses of its separate constituents. In a nucleus, it corresponds to the energy released when nucleons bind, divided by the speed of light squared.

Nuclear binding energy: The energy required to separate an atomic nucleus completely into its constituent protons and neutrons. Nuclear mass defect gives this energy through Einstein’s mass–energy relation.
Atomic nucleus: The small, dense central region of an atom, composed of protons and neutrons. Nuclear mass defect compares its mass with the masses of its separate nucleons.
Nuclear fission: A nuclear reaction in which a heavy nucleus splits into lighter nuclei, often releasing energy. The products’ lower total mass accounts for the energy released in fission.
Mass excess: The difference between a nuclide’s mass and its mass number expressed in atomic mass units. It uses a reference mass based on nucleon count, not the sum of free constituent masses.
Einstein mass–energy equivalence: The principle that mass and energy are equivalent, related by the equation E = mc². It converts the mass difference between bound and free nucleons into binding energy.
Proton: A positively charged subatomic particle found in atomic nuclei. Its mass is one of the constituent masses summed for a nucleus.
Nuclear fusion: A nuclear reaction in which light nuclei combine to form a heavier nucleus. Fusion releases energy when the product nucleus has a greater mass defect per nucleon.
Mass deficit: A general shortfall in mass relative to a stated reference or expected total. The phrase can describe a comparison, but does not by itself specify nuclear binding.
Nuclear force: The residual strong interaction that binds protons and neutrons inside atomic nuclei. Its attractive energy lowers a nucleus’s mass relative to separated nucleons.
Neutron: A subatomic particle with no electric charge, found in atomic nuclei. Its mass completes the constituent-mass sum for a nucleus.

Linked from 9 pages