An Atomic Number (Z) is a number of protons in the nucleus of an atom determines an element’s atomic number. The Atomic Number identifies a chemical element, and is equal to the number of electrons in an uncharged atom. The Atoms of different elements have different numbers of protons. For example, all oxygen atoms have 8 protons and all sodium atoms have 11 protons. The mass number of an atom is the total number of protons and neutrons it contains. The mass number of an atom is never smaller than the atomic number.
Related Definitions in the Project: The Property and Unit
