A nuclide (from nucleus, originally from Latin, meaning kernel of a nut)'s an atomic nucleus characterized by its specific constitution, for example, by its number of protons, its number of neutrons, and its energy content. The various nuclides, or species, of a particular chemical element with equal proton number (atomic number), but different neutron numbers were called isotopes of the element, before the more inclusive term "nuclide" was internationally accepted (ca. 1950. Such particular nuc… (More on Nuclide)