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Deuterium (hydrogen-2, symbol 2 H or D, also known as heavy hydrogen) is one of two stable isotopes of hydrogen; the other is protium, or hydrogen-1, 1 H. The deuterium nucleus ( deuteron ) contains one proton and one neutron , whereas the far more common 1 H has no neutrons.
Deuterium, 2 H (atomic mass 2.014 101 777 844 (15) Da), the other stable hydrogen isotope, has one proton and one neutron in its nucleus, called a deuteron. 2 H comprises 26–184 ppm (by population, not mass) of hydrogen on Earth; the lower number tends to be found in hydrogen gas and higher enrichment (150 ppm) is typical of seawater .
Heavy water (deuterium oxide, 2 H 2 O, D 2 O) is a form of water in which hydrogen atoms are all deuterium (2 H or D, also known as heavy hydrogen) rather than the common hydrogen-1 isotope (1 H, also called protium) that makes up most of the hydrogen in normal water. [3]
Deuterium (2 H) is the most easily fused nucleus available to accreting protostars, [1] and such fusion in the center of protostars can proceed when temperatures exceed 10 6 K. [2] The reaction rate is so sensitive to temperature that the temperature does not rise very much above this. [2]
Water samples made up of different isotopes of hydrogen and oxygen have slightly different physical properties. As an extreme example, heavy water, which contains two deuterium (2 H) atoms instead of the usual, lighter hydrogen-1 (1 H), has a melting point of 3.82 °C (38.88 °F) and boiling point of 101.4 °C (214.5 °F). [1]
All isotopes of an element have the same number of protons with varying numbers of neutrons. Hydrogen has three naturally occurring isotopes: 1 H, 2 H and 3 H; called protium (H), deuterium (D) and tritium (T), respectively. Both 1 H and 2 H are stable, while 3 H is unstable and beta-decays to 3 He.
Deuterium is stable, makes up 0.0156% of naturally occurring hydrogen, [2] and is used in industrial processes like nuclear reactors and Nuclear Magnetic Resonance. Tritium ( 3 H) contains two neutrons and one proton in its nucleus and is not stable, decaying with a half-life of 12.32 years.
Semiheavy water is the result of replacing one of the protium (normal hydrogen, 1 H) in normal water with deuterium (2 H; or less correctly, [1] D). [2] It exists whenever there is water with 1 H and 2 H in the mix. This is because hydrogen atoms (1,2 H) are rapidly exchanged between water molecules.