nuclide

The term nuclide (or nuclear species) refers to an atomic nucleus that has specific numbers of protons and neutrons. Equivalently, it is a nucleus with a specific atomic number (Z) and mass number (A). A different (type of) nuclide would imply a different isotope or a different element. The term is common in descriptions of nucleosynthesis (the construction or modification of a nucleus) if the specific number of electrons is not relevant.

There may be more than one possible arrangement of the protons and neutrons in a nuclide, and the term nuclear isomer refers to a specific arrangement (typically associated with an energy level of the nucleus). Some of a nuclide's nuclear isomers are more stable than others, and after a nuclear reaction producing one, it may later settle into the more stable configuration, yet remain the same nuclide and isotope. Such settling releases energy which may take the form of a gamma-ray photon or if an atom, it may eject one of its electrons.

Wikipedia now explains usages of nuclide that differ slightly from the above description:

• the term is also used for atoms that incorporate the particular type of nucleus, though Wikipedia says the term was initially coined to refer to nuclei.
• different nuclear isomers are considered different nuclides.