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Hydrogen (1 H) has three naturally occurring isotopes: 1 H, 2 H, and 3 H. 1 H and 2 H are stable, while 3 H has a half-life of 12.32(2) years. [3] [nb 1] Heavier isotopes also exist; all are synthetic and have a half-life of less than 1 zeptosecond (10 −21 s). [4] [5] Of these, 5 H is the least stable, while 7 H is the most.
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 occurs in trace amounts naturally as deuterium gas (2 H 2 or D 2), but most deuterium atoms in the Universe are bonded with 1 H to form a gas called hydrogen deuteride (HD or 1 H 2 H). [12] Similarly, natural water contains deuterated molecules, almost all as semiheavy water HDO with only one deuterium.
H), deuterium (2 H), and tritium (3 H), because deuterium has twice the mass of protium and tritium has three times the mass of protium. [33] These mass differences also affect the behavior of their respective chemical bonds, by changing the center of gravity (reduced mass) of the atomic systems. However, for heavier elements, the relative mass ...
Normal hydrogen (protium, 1 H) has no neutron. Deuterium (2 H) has one neutron, and tritium (3 H) has two. Neutrons add mass to the atom, leading to different chemical physical properties. This effect is especially strong for hydrogen isotopes, since the added neutron doubles the mass from 1 H to 2 H.
Hydrogen deuteride is an isotopologue of dihydrogen composed of two isotopes of hydrogen: the majority isotope 1 H and 2 H . Its proper molecular formula is 1 H 2 H, but for simplification, it is usually written as HD.
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.
Depending on the formula and the symmetry of the structure, there might be several isotopomers of one isotopologue. For example, ethanol has the molecular formula C 2 H 6 O. Mono-deuterated ethanol, C 2 H 5 DO or C 2 H 5 2 HO, is an isotopologue of it. The structural formulas CH 3 −CH 2 −O−D and CH 2 D−CH 2 −O−H are two isotopomers ...