Atomic Structure and Isotopes

Key vocabulary terms and definitions covering atomic structure, mass number, isotopes, and relative atomic mass.

Atomic number ($Z$)

The number of protons in the nucleus of an atom, which determines which element it is; in a neutral atom, it is equal to the number of electrons.

Mass number ($A$)

The sum of protons and neutrons found in the nucleus of an atom, which determines the mass of an atom.

Isotopes

Atoms of the same element with an equal number of protons but a different number of neutrons, which differ in relative atomic mass but not in chemical properties.

Relative atomic mass

The average mass of all the different isotopes of an element.