Hydrogen (H) (Standard atomic mass: 1.00794(7) u) has three naturally occurring isotopes, denoted 1H, 2H, and 3H. Other, highly unstable nuclei (4H to 7H) have been synthesized in the laboratory but not observed in nature.[1][2]
Hydrogen is the only element that has different names for its isotopes in common use today. (During the early study of radioactivity, various heavy radioactive isotopes were given names; but such names are rarely used today). The symbols D and T (instead of 2H and 3H) are sometimes used for deuterium and tritium. IUPAC states that while this use is common it is not preferred.
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Hydrogen-1 (protium)
1H is the most common hydrogen isotope with an abundance of more than 99.98%. Because the nucleus of this isotope consists of only a single proton, it is given the descriptive but rarely used formal name protium.
Hydrogen-2 (deuterium)
2H, the other stable hydrogen isotope, is known as deuterium and contains one proton and one neutron in its nucleus. Deuterium comprises 0.0026 – 0.0184% (by population, not by mass) of hydrogen samples on Earth, with the lower number tending to be found in samples of hydrogen gas and the higher enrichments (0.015% or 150 ppm) typical of ocean water. Deuterium is not radioactive, and does not represent a significant toxicity hazard. Water enriched in molecules that include deuterium instead of normal hydrogen is called heavy water. Deuterium and its compounds are used as a non-radioactive label in chemical experiments and in solvents for 1H-NMR spectroscopy. Heavy water is used as a neutron moderator and coolant for nuclear reactors. Deuterium is also a potential fuel for commercial nuclear fusion.
Hydrogen-3 (tritium)
3H is known as tritium and contains one proton and two neutrons in its nucleus. It is radioactive, decaying into helium-3 through β− decay with a half-life of 12.32 years.[3] Small amounts of tritium occur naturally because of the interaction of cosmic rays with atmospheric gases; tritium has also been released during nuclear weapons tests. It is used in thermonuclear fusion weapons, as a tracer in isotope geochemistry, and specialized in self-powered lighting devices. Tritium was once routinely used in chemical and biological labelling experiments as a radiolabel (this has become less common). D-T nuclear fusion uses tritium as its main reactant, along with deuterium, liberating energy through the loss of mass when the two nuclei collide and fuse under massive temperatures.
Hydrogen-4
4H is a highly unstable isotope of hydrogen. The nucleus consists of a proton and three neutrons. It has been synthesised in the laboratory by bombarding tritium with fast-moving deuterium nuclei.[4] In this experiment, the tritium nuclei captured neutrons from the fast-moving deuterium nucleus. The presence of the hydrogen-4 was deduced by detecting the emitted protons. Its atomic mass is 4.02781 ± 0.00011.[5] It decays through neutron emission and has a half-life of (1.39 ± 0.10) × 10−22 seconds.[6]
Hydrogen-5
5H is a highly unstable isotope of hydrogen. The nucleus consists of a proton and four neutrons. It has been synthesised in the laboratory by bombarding tritium with fast-moving tritium nuclei.[4][7] In this experiment, one tritium nucleus captures two neutrons from the other, becoming a nucleus with one proton and four neutrons. The remaining proton may be detected, and the existence of hydrogen-5 deduced. It decays through double neutron emission and has a half-life of at least 9.1 × 10−22 seconds.[6]
Hydrogen-6
6H decays through triple neutron emission and has a half-life of 3×10−22 seconds. It consists of 1 proton and 5 neutrons.
Hydrogen-7
7H consists of a proton and six neutrons. It was first synthesised in 2003 by a group of Russian, Japanese and French scientists at RIKEN's RI Beam Science Laboratory by bombarding hydrogen with helium-8 atoms. In the resulting reaction, the helium-8's neutrons were donated to the hydrogen's nucleus. The two remaining protons were detected by the "RIKEN telescope", a device composed of several layers of sensors, positioned behind the target of the RI Beam cyclotron[8].
Hydrogen-like exotic atoms
- Positronium (Ps or e+e−)
Positronium is an exotic atom made up of a positron (the electron's antiparticle, also called antielectron) and an electron, and is given the symbol Ps or e+e−. It decays to 2 or more photons (in the form of gamma radiation) due to annihilation.
- Muonium (Mu or µ+e−)
Muonium is an exotic atom made up of an antimuon (the muon's antiparticle) and an electron,[9] and is given the symbol Mu or µ+e−. During the muon's 2.2 µs lifetime, muonium can enter into compounds such as muonium chloride (MuCl) or sodium muonide (NaMu).[10]
- Antihydrogen (H)
Antihydrogen is the antimatter counterpart of hydrogen. Whereas the common hydrogen atom is composed of an electron and proton, the antihydrogen atom is made up of a positron (also called antielectron) and an antiproton.
Table
| Nuclide | Z(p) | N(n) | mass (u)[n 2] | half-life | nuclear spin ( J P )[n 3] |
RIC [n 4] (mole fraction) |
RNV [n 5] (mole fraction) |
|---|---|---|---|---|---|---|---|
| 1H | 1 | 0 | 1.00782503207(10) | Stable[n 6] | 1⁄2+ | 0.999885(70) | 0.999816–0.999974 |
| 2H | 1 | 1 | 2.0141017778(4) | Stable | 1+ | 0.000115(70)[n 7] | 0.000026–0.000184 |
| 3H | 1 | 2 | 3.0160492777(25) | 12.32(2) a | 1⁄2+ | ||
| 4H | 1 | 3 | 4.02781(11) | 1.39(10)×10−22 s [4.6(9) MeV] | 2− | ||
| 5H | 1 | 4 | 5.03531(11) | >9.1×10−22 s ? | (1⁄2+) | ||
| 6H | 1 | 5 | 6.04494(28) | 2.90(70)×10−22 s [1.6(4) MeV] | 2− [n 8] | ||
| 7H | 1 | 6 | 7.05275(108) [n 8] | 2.3(6)×10−23 s [n 8] [20(5) MeV] [n 8] | 1/2+ [n 8] |
- Notes
- ^ Commercially available materials may have been subjected to an undisclosed or inadvertent isotopic fractionation. Substantial deviations from the given mass and composition can occur.
- ^ Uncertainties are given in concise form in parentheses after the corresponding last digits, and denote one standard deviation.
- ^ Spins with weak assignment arguments are enclosed in parentheses.
- ^ Representative isotopic composition (RIC): refers to that in water.
- ^ Range of natural variation (RNV): The precision of the isotope abundances and atomic mass is limited through variations. The given ranges should be applicable to any normal terrestrial material.
- ^ Greater than 6.6×1033 a. See proton decay.
- ^ Tank hydrogen has a 2H abundance as low as 3.2×10−5 (mole fraction).
- ^ a b c d e Value is not purely derived from experimental data, but at least partly from systematic trends.
References
- Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
- Isotopic compositions and standard atomic masses from Atomic weights of the elements. Review 2000 (IUPAC Technical Report). Pure Appl. Chem. Vol. 75, No. 6, pp. 683-800, (2003) and Atomic Weights Revised (2005).
- Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
- Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties, Nuc. Phys. A 729, pp. 3-128 (2003).
- National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database (retrieved Sept. 2005).
- David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.
- ^ Gurov YB, Aleshkin DV, Berh MN, Lapushkin SV, Morokhov PV, Pechkurov VA, Poroshin NO, Sandukovsky VG, Tel'kushev MV, Chernyshev BA, Tschurenkova TD. (2004). Spectroscopy of superheavy hydrogen isotopes in stopped-pion absorption by nuclei. Physics of Atomic Nuclei 68(3):491–497.
- ^ Korsheninnikov AA. et al. (2003). Experimental Evidence for the Existence of 7H and for a Specific Structure of 8He. Phys Rev Lett 90, 082501.
- ^ Miessler GL, Tarr DA. (2004). Inorganic Chemistry 3rd ed. Pearson Prentice Hall: Upper Saddle River, NJ, USA
- ^ a b Hydrogen-4 and Hydrogen-5 from t+t and t+d transfer reactions studied with a 57.5-MeV triton beam, G. M. Ter-Akopian et al., Nuclear Physics in the 21st Century: International Nuclear Physics Conference INPC 2001, American Institute of Physics Conference Proceedings 610, pp. 920-924, doi:10.1063/1.1470062.
- ^ AME2003 atomic mass evaluation, Atomic Mass Data Center. Accessed on line November 15, 2008.
- ^ a b p. 27, The NUBASE evaluation of nuclear and decay properties, G. Audi, O. Bersillon, J. Blachot, and A. H. Wapstra, Nuclear Physics A 729 (2003), pp. 3–128.
- ^ Korsheninnikov, A. A.; M. S. Golovkov, I. Tanihata, A. M. Rodin, A. S. Fomichev, S. I. Sidorchuk, S. V. Stepantsov, M. L. Chelnokov, V. A. Gorshkov, D. D. Bogdanov (2001). "Superheavy Hydrogen 5H". Physical Review Letters 87 (9): 92501. doi:.
- ^ Korsheninnikov, A. A.; E. Y. Nikolskii, E. A. Kuzmin, A. Ozawa, K. Morimoto, F. Tokanai, R. Kanungo, I. Tanihata, N. K. Timofeyuk, M. S. Golovkov (2003). "Experimental Evidence for the Existence of 7H and for a Specific Structure of 8He". Physical Review Letters 90 (8): 82501. doi:.
- ^ International Union of Pure and Applied Chemistry. "muonium". Compendium of Chemical Terminology Internet edition.
- ^ "Names for muonium and hydrogen atoms and their ions" (PDF). IUPAC. 2001. http://www.iupac.org/publications/pac/2001/pdf/7302x0377.pdf.
In fiction
In the 1955 satirical novel The Mouse That Roared, the name quadium was given to the hydrogen-4 isotope that powered the Q-bomb that the Duchy of Grand Fenwick captured from the United States.
External links
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- News of hydrogen-7 discovery
- Article on hydrogen-4 and hydrogen-5 (login required)
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