Nuclide
A distinct species of atom characterised by a specific number of protons and neutrons in its nucleus.
Formula / equation
ᴬ_Z X
Unit
Dimensionless
In depth
The term nuclide emphasises the nucleus rather than the chemical element, which is why it is preferred in nuclear science. About 250 nuclides are stable, while more than three thousand radioactive ones have been identified or synthesised.
Examples in the real world
Carbon-12 and carbon-14 are different nuclides of the same element; uranium-235 and uranium-238 likewise.