nuclide

https://dx.doi.org/10.1351/goldbook.N04257
A species of atom, characterized by its mass number, atomic number and nuclear energy state, provided that the mean life in that state is long enough to be observable.
Source:
PAC, 1994, 66, 2513 (Nomenclature for radioanalytical chemistry (IUPAC Recommendations 1994)) on page 2522
PAC, 1982, 54, 1533 (Glossary of terms used in nuclear analytical chemistry (Provisional)) on page 1547