Isotopes of Hydrogen

If atoms of the same element have different mass numbers they are called isotopes. This difference in mass number arises because the nucleus contains a different number of neutrons.

Naturally occurring hydrogen contains three isotopes:

1. Protium ¹₁H or H
2. Deuterium ²₁H or D
3. Tritium ³₁H or T

These three isotopes contain one proton and 0, 1 and 2 neutrons, respectively in the nucleus. Protium is by far the most abundant.