Deuterium

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Template:Stable Isotope Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance of one atom in 6500 of hydrogen. The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas a normal hydrogen nucleus contains only a proton and no neutrons.

The chemical symbol ²H identifies deuterium. The unofficial symbol D is also often used, even though deuterium is not a chemical element in its own right. It occurs as deuterium gas, written ²H₂ or D₂, but most natural occurance in the universe is bonded with a typical ¹H atom, a gas called hydrogen deuteride.<ref>Template:Cite journal</ref>

The two isotopes can be distinguished physically by using mass spectrometry. In addition, the physical properties of deuterium compounds can be different than the hydrogen analogs; for example, D₂O is more viscous than H₂O. The deuteron has spin +1 and is thus a boson.

Deuterium behaves chemically similarly to ordinary hydrogen, but there are differences in bond energy and length for compounds of heavy hydrogen isotopes which are larger than the isotopic differences in any other elements. Bonds involving deuterium and tritium are somewhat stronger than the corresponding bonds in light hydrogen, and these differences are enough to make significant changes in biological reactions (see heavy water).

Deuterium can replace the normal hydrogen in water molecules to form heavy water (D₂O), which is about 10% more dense than normal water. Heavy water is modestly toxic in eukariotic animals, with 25% substitution of the body water causing cell division problems and sterility, and 50% substitution causing death by cytotoxic syndrome (bone marrow failure and gastrointestinal lining failure). Bacteria, however, can survive and grow in pure heavy water. Consumption of heavy water would not pose a health threat to humans unless very large quantities (in excess of 10 liters) were consumed over many days. Small doses of heavy water (a few grams) are routinely used as harmless metabolic tracers in humans and animals.

The existence of deuterium in stars is an important datum in cosmology. Stellar fusion destroys deuterium, and there are no known natural processes, other than the Big Bang nucleosynthesis, which produce deuterium. Thus, the existence of deuterium is one of the arguments in favour of the Big Bang theory over the steady state theory of the universe.

The world's leading producer of deuterium is Canada, in the form of heavy water as neutron moderator for the operation of the CANDU reactor.

1 Applications
2 History
3 Data
4 Anti-deuterium
5 References

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Applications

Deuterium is useful in nuclear fusion reactions, especially in combination with tritium, because of the large reaction rate (or cross section) and high energy yield of the D-T reaction. Unlike protium, deuterium undergoes fusion via the strong interaction, making its use for commercial power plausible.

In chemistry and biochemistry, deuterium is used in tracer molecules to study chemical reactions and metabolic pathways because chemically it behaves similarly to ordinary hydrogen, but it can be distinguished from ordinary hydrogen by its mass using mass spectrometry.

Deuterium is particlarly useful in hydrogen nuclear magnetic resonance (1H-NMR). Because of its different nuclear spin properties from the hydrogen generally connected to molecules, spectra of hydrogen are highly differentiable from that of deuterium. Deuterium can also be used for femtosecond IR spectroscopy, since the mass difference drastically affects the frequency of molecular vibrations; deuterium-carbon bond vibrations are found in locations free of other signals.

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History

The existence of nonradioactive isotopes of lighter elements had been suspected in studies of neon as early as 1913, and proven by mass spectroscopy in 1920. The prevailing theory, however, was that these were due to the existence of differing numbers of "nuclear electrons." It was expected that hydrogen, with a nucleus composed only of a proton and with a measured average atomic mass very close to 1, could not contain nuclear electrons and thus have no heavy isotopes.

Deuterium was predicted in 1926 by Walter Russell, using his "spiral" periodic table, and first detected in late 1931 by Harold Urey, a chemist at Columbia University. Urey distilled 5 liters of liquid hydrogen to 1 milliliter of liquid and showed spectroscopically that it contained a very small amount of isotope of hydrogen with an atomic mass of 2, and called the isotope "deuterium" from the Greek word for "two." The amount was so small that it did not affect atomic mass average. Urey was also able to concentrate water to show enrichment of this heavy isotope of hydrogen (Gilbert Newton Lewis prepared the first pure samples of heavy water in 1933, see heavy water). The discovery of deuterium, coming before the discovery of the neutron in 1932, was an experimental shock to theory, and it won Urey the Nobel Prize in chemistry in 1934.

For the history of heavy water see that topic. During World War II, Nazi Germany was known to be conducting experiments using heavy water as moderator for a nuclear reactor design. This was a source of concern because it might allow them to produce plutonium for an atomic bomb. Ultimately, it led to a seemingly important Allied operation, the Norwegian heavy water sabotage, to destroy the Vemork deuterium production facility in Norway. It turned out, however, that Germany was not putting any serious efforts into the program, and only had a small partly-built experimental reactor hidden away. In reality the Germans did not even have a fifth the amount of heavy water needed to run the reactor, partially due to the Norwegian heavy water sabotage operation.-->

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Data

density: 0.180 kg/m³ at STP (0 °C, 101.325 kPa).
atomic weight: 2.01355321270.

Data at approximately 18 K for D₂ (triple point):

density:

solid: 195 kg/m³
gas: 0.452 kg/m³

viscosity: 1.3 µPa·s
specific heat capacity at constant pressure c_p:

solid: 2950 J/(kg·K)
gas: 5200 J/(kg·K)

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Anti-deuterium

An antideuteron is the antiparticle of the nucleus of deuterium, consisting of an antiproton and an antineutron. The antideuteron was first produced at CERN and the Brookhaven National Laboratory in 1965. A complete atom, with a positron orbiting the nucleus, would be called antideuterium, but as of 2005 antideuterium has not yet been created. The symbol for antideuterium is the same as for deuterium, except with a bar over it.

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