Isotopes of hydrogen

<p><a href="/facts/Hydrogen/BoYHjl0J">Hydrogen</a> (1H) has three naturally occurring <a href="/facts/Isotope/KD9B1y6o">isotopes</a>: 1H, 2H, and 3H. 1H and 2H are stable, while 3H has a <a href="/facts/Half-life/kGVH8BAB">half-life</a> of 12.33(2) years. Heavier isotopes also exist; all are synthetic and have a half-life of less than 1 <a href="/facts/Zeptosecond/bEovB6Tp">zeptosecond</a> (10−21 s).
Of these, 5H is the least stable, while 7H is the most.
</p><p>Hydrogen is the only <a href="/facts/Chemical_element/0jducgWD">element</a> whose isotopes have different names that remain in common use today: 2H is <a href="/facts/Deuterium/Bv4wfCkw">deuterium</a> and 3H is <a href="/facts/Tritium/HWSa6EHy">tritium</a>. The symbols D and T are sometimes used for deuterium and tritium; IUPAC (<a href="/facts/International_Union_of_Pure_and_Applied_Chemistry/2AV6myCK">International Union of Pure and Applied Chemistry</a>) accepts said symbols, but recommends the standard isotopic symbols 2H and 3H, to avoid confusion in alphabetic sorting of <a href="/facts/Chemical_formula/hghUtthl">chemical formulas</a>. 1H, with no <a href="/facts/Neutron/oRCM1geb">neutrons</a>, may be called protium to disambiguate. (During the early study of radioactivity, some other heavy radioisotopes were given <a href="/facts/Chemical_symbol/2Fe1VAL0">names</a>, but such names are rarely used today.)
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Isotopes of hydrogen open-in-new

Isotopes of hydrogen