Isotopes of hydrogen
Hydrogen has three main isotopes; protium (1H), deuterium (2H) and tritium (3H). These isotopes form naturally in nature. Protium and deuterium are stable. Tritium is radioactive and has a half-life of about 12 years. Scientists have created four other hydrogen isotopes (4H to 7H), but these isotopes are very unstable and do not exist naturally.