Deuterium

Deuterium (hydrogen-2, symbol 2H or D, also known as heavy hydrogen) is one of two <a href="/facts/Stable_isotope_ratio/vgcdxgjA">stable isotopes</a> of <a href="/facts/Hydrogen/BoYHjl0J">hydrogen</a>; the other is protium, or hydrogen-1, 1H. The deuterium <a href="/facts/Atomic_nucleus/orpIm5Xl">nucleus</a> (deuteron) contains one <a href="/facts/Proton/clCjepXP">proton</a> and one <a href="/facts/Neutron/oRCM1geb">neutron</a>, whereas the far more common 1H has no neutrons. 
The name deuterium comes from Greek deuteros, meaning "second". American chemist <a href="/facts/Harold_Urey/j1bPXfDz">Harold Urey</a> discovered deuterium in 1931. Urey and others produced samples of <a href="/facts/Heavy_water/3dbSrTw5">heavy water</a> in which the 2H had been highly concentrated. The discovery of deuterium won Urey a <a href="/facts/List_of_Nobel_laureates_in_Chemistry/7osWRyAd">Nobel Prize</a> in 1934.
Nearly all deuterium found in nature was <a href="/facts/Big_Bang_nucleosynthesis/IvM4gbKH">synthesized in</a> the <a href="/facts/Big_Bang/I5T1vTnv">Big Bang</a> 13.8 billion years ago, forming the primordial ratio of 2H to 1H (~26 deuterium nuclei per 106 hydrogen nuclei). Deuterium is subsequently produced by the slow stellar <a href="/facts/Proton%25E2%2580%2593proton_chain/UUDAR9yW">proton–proton chain</a>, but rapidly destroyed by exothermic <a href="/facts/Nuclear_fusion/hP0gLDqj">fusion reactions</a>. The <a href="/facts/Deuterium-deuterium_fusion/ngGwwfoV">deuterium–deuterium reaction</a> has the second-lowest <a href="/facts/Lawson_criterion/aPUrM8Tp">energy threshold</a>, and is the most astrophysically accessible, occurring in both <a href="/facts/Stars/euBFuo07">stars</a> and <a href="/facts/Brown_dwarfs/fa7kr9lH">brown dwarfs</a>.
The <a href="/facts/Gas_giant/pmF6KztG">gas giant</a> planets display the primordial ratio of deuterium. Comets show an elevated ratio similar to Earth's oceans (156 deuterium nuclei per 106 hydrogen nuclei). This reinforces theories that much of Earth's ocean water is of cometary origin. The deuterium ratio of comet <a href="/facts/67P%2fChuryumov%25E2%2580%2593Gerasimenko/FBdA81uy">67P/Churyumov–Gerasimenko</a>, as measured by the <a href="/facts/Rosetta_(spacecraft)/ASd7ggs3">Rosetta</a> space probe, is about three times that of Earth water. This figure is the highest yet measured in a comet, thus deuterium ratios continue to be an active topic of research in both astronomy and climatology.
Deuterium is used in most <a href="/facts/Nuclear_weapon/QVdBcMdm">nuclear weapons</a>, many <a href="/facts/Fusion_power/jyETSzm4">fusion power</a> experiments, and as the most effective <a href="/facts/Neutron_moderator/1qa6YvDD">neutron moderator</a>, primarily in <a href="/facts/Pressurized_heavy-water_reactor/YfjI0tqR">heavy water nuclear reactors</a>. It is also used as an <a href="/facts/Isotopic_label/Sqtr7c0G">isotopic label</a>, in <a href="/facts/Hydrogen_isotope_biogeochemistry/uTY1yDa8">biogeochemistry</a>, <a href="/facts/Deuterium_NMR/3GULu1yC">NMR spectroscopy</a>, and <a href="/facts/Deuterated_drug/zr5zcBRS">deuterated drugs</a>.

Deuterium open-in-new

Deuterium