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Isotopes
Main article: Isotopes of hydrogen
Hydrogen is the only element that has different names for its isotopes. (During the early study of radioactivity, various heavy radioactive isotopes were given names, but such names are no longer used, although one element, radon, has a name that originally applied to only one of its isotopes.) The symbols D and T (instead of 2H and 3H) are sometimes used for deuterium and tritium, although this is not officially sanctioned. (The symbol P is already in use for phosphorus and is not available for protium.)

1H
The most common isotope of hydrogen, this stable isotope has a nucleus consisting of a single proton; hence the descriptive, although rarely used, name protium. The spin of a protium atom is 1/2+. [5]

2H
The other stable isotope is deuterium, with an extra neutron in the nucleus. Deuterium comprises 0.0184%–0.0082% of all hydrogen on Earth (IUPAC); ratios of deuterium to protium are reported relative to the VSMOW standard reference water. The spin of a deuterium atom is 1+.

3H
The third naturally occurring hydrogen isotope is the radioactive tritium. The tritium nucleus contains two neutrons in addition to the proton. It decays through beta decay and has a half-life of 12.32 years. Tritium occurs naturally due to cosmic rays interacting with atmospheric gases. Like ordinary hydrogen, tritium reacts with the oxygen in the atmosphere to form T2O. This radioactive "water" molecule constantly enters the Earth's seas and lakes in the form of slightly radioactive rain, but its half-life is short enough to prevent a buildup of hazardous radioactivity. The spin of a tritium atom is 1/2+.

4H
Hydrogen-4 was synthesized by bombarding tritium with fast-moving deuterium nuclei. It decays through neutron emission and has a half-life of 9.93696x10−23 seconds. The spin of a hydrogen-4 atom is 2-.

5H
In 2001 scientists detected hydrogen-5 by bombarding a hydrogen target with heavy ions. It decays through neutron emission and has a half-life of 8.01930x10−23 seconds.

6H
Hydrogen-6 decays through triple neutron emission and has a half-life of 3.26500x10−22 seconds.

7H
In 2003 hydrogen-7 was created (article) at the RIKEN laboratory in Japan by colliding a high-energy beam of helium-8 atoms with a cryogenic hydrogen target and detecting tritons—the nuclei of tritium atoms—and neutrons from the breakup of hydrogen-7, the same method used to produce and detect hydrogen-5.

Biology
Scientists from the University of Colorado at Boulder discovered in 2005 that microbes living in the hot waters of Yellowstone National Park gain their sustenance from molecular hydrogen.

See also
Antihydrogen
Deuterium
Fuel cell
Hydrogen atom
Hydrogen bomb
Hydrogen bond
Hydrogen vehicle
Hydrogen cycle
Hydrogen economy
Hydrogen line
Hydrogen molecule
Hydrogen spectral series
Hydrogen station
Liquid hydrogen
Natural gas
Photohydrogen
Tritium
References
^ Los Alamos National Laboratory – Hydrogen. URL accessed on September 15, 2005.
^ Webelements – Hydrogen historical information. URL accessed on September 15, 2005.
^ Jefferson Lab – Hydrogen. URL accessed on September 15, 2005.
^ Universal Industrial Gases, Inc. – Hydrogen (H2) Applications and Uses. URL accessed on September 15, 2005.
^ Lawrence Berkeley National Laboratory – Hydrogen isotopes. URL accessed on September 15, 2005.
RIKEN Beam Science Laboratory, Japan — Heavy hydrogen research
Nuclides and Isotopes Fourteenth Edition: Chart of the Nuclides, General Electric Company, 1989
Book references
Stwertka, Albert (2002). A Guide to the Elements. New York, NY: Oxford University Press. ISBN 0195150279.
Krebs, Robert E. (1998). The History and Use of Our Earth's Chemical Elements : A Reference Guide. Westport, Conn.: Greenwood Press. ISBN 0313301239.
Newton, David E. (1994). The Chemical Elements. New York, NY: Franklin Watts. ISBN 0531125017.
Rigden, John S. (2002). Hydrogen : The Essential Element. Cambridge, MA: Harvard University Press. ISBN 0531125017.
Other references
"New Trends in Reforming Technologies: from Hydrogen Industrial Plants to Multifuel Microreformers" P. Ferreira-Aparicio, M. J. Benito, J. L. Sanz Catalysis Reviews, volume 47, pages 491–588, 2005.