Posted on

Atomic Number, Mass Number, Isotopes, and Relative Atomic Masses of Atoms

Atomic number
This is the number of protons (i e. number of positive charges) in the nucleus of any atom.

Mass number
This is the total number of protons and neutrons (collectively called nucleons) in the nucleus of the atom.

Isotopes are atoms of the same elements with the same atomic number but different mass numbers. The isotope of an element whose symbol is X can be represented as shown.

Example: Two isotopes of chlorine are img 5 and img 6