Nuclide

Nuclide, also called nuclear species, species of atom as characterized by the number of protons, the number of neutrons, and the energy state of the nucleus.

A nuclide is characterized by the mass number (A) and the atomic number (Z).

$ _{Z}^{A} X$, where

X = symbol of the element
A = nucleon number (AKA mass number)
Z = proton number (AKA atomic number)

Each species of atom has its own name and chemical symbol. Most symbols are based on either English or Latin names. The symbol will have a capital letter and may be followed by a small cap letter.

Recall: Number of neucleons = number of protons + number of neutrons