The isotopes of hydrogen are :

Isotopes are the ones that has the same atomic number but different mass number. There are three isotopes of hydrogen:

Protium $\left({}_1{}^1\mathrm{H}\right),$ Deuterium $\left({}_1{}^2\mathrm{H}\right),$ and Tritium $\left({}_1{}^3\mathrm{H}\right).$