Atomic mass also called the mass number of an atom.
Explanation;
Mass number or the atomic mass is the number of protons and neutrons in an atom, and it tells us about the mass of the atom in amu, or atomic mass units. The number of neutrons can vary to produce isotopes, which are atoms of the same element that have different numbers of neutrons.
The atomic number or proton number (symbol Z) of a chemical element is the number of protons found in the nucleus of an atom. It is identical to the charge number of the nucleus
