Hydrogen has three naturally occuring isotopes. They are 1H1, 2H1 (also called "deuterium") and 3H1 (known as "tritium"). Of the three, 1H1 is the most abundant, with deuterium occuring in about a 1:6500 ratio with 1H1, and tritium in about a 1:1018 ratio.

Tritium is the most interesting since it's radioactive. Tritium has a half-life of 12.4 years and breaks down like this:

3H1 --> 3He2 + 0e-1

where 0e-1 is a beta particle (electron) and 3He2 is helium.

You can produce tritium at home by bombarding lithium with neutrons to make tritium and helium.

6Li3 + 1n0 --> 3H1 + 4He2

This is one of the reactions that take place when a hydrogen bomb explodes.

H-5 discovered

This is an update on the current state of the art concerning hydrogen.

The commonly known isotopes of hydrogen are:

  • Hydrogen-1, the "normal" and most abundant variety,
  • Hydrogen-2, known as deuterium, and
  • Hydrogen-3, known as tritium.
Isotopes, of course, are "variants" of an element with different numbers of neutrons in the nucleus. H-1 has a lone proton, H-2 has a proton and one neutron, H-3 has a proton and two neutrons.

Deuterium and tritium are constituents of heavy water. Tritium is radioactive. Both are much rarer than H-1 and play a role in the development both of the hydrogen bomb and of nuclear fusion reactors.

Atom-smashing equipment, in particular particle accelerators, enable physicists to create some isotopes which do not occur in nature. Apparently they've already produced H-4, a synthetic isotope with 3 neutrons in the nucleus, but I haven't come across any exciting information about this. The big news is H-5.

Late in 2001, an international group of researchers collided a beam of helium-6 nuclei into a target of cryogenic (frozen) hydrogen. In the ensuing nuclear reaction, it's possible for the He-6 to transfer all 4 of its neutrons to the hydrogen, turning it into - Hydrogen-5. Of course the experiment, which took place at the RIKEN detector in Japan, produced only trace quantities of the highly unstable isotope; and rather than collecting some of the product, the researchers obtained only indirect evidence of the production of this isotope. Still, it's considered a major breakthrough in nuclear physics, as the search for H-5 had been ongoing for 40 years previously.

  • http://www.spiegel.de/wissenschaft/mensch/0,1518,151441,00.html
  • http://physicsweb.org/article/news/5/8/15

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