Atomic Number Definition

noun

The number of protons in an atomic nucleus.

American Heritage

A number representing the relative position of an element in the periodic table, in which the elements are arranged in the order of their nuclear charges; a number representing the positive charge or the number of protons in the nucleus of the atom of an element: isotopes have the same atomic number but different mass numbers.

Webster's New World

(physics, chemistry) The number, equal to the number of protons in an atom that determines its chemical properties. Symbol: Z.

Wiktionary

Attributive form of atomic number.

Atomic-number data.

Wiktionary