Transuranium element

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The transuranium elements (also known as transuranic elements) are the chemical elements with atomic numbers greater than 92 (the atomic number of uranium). All of these elements are unstable and decay radioactively into other elements.

Overview[edit]

Periodic table with elements colored according to the half-life of their most stable isotope.
  Elements which contain at least one stable isotope.
  Slightly radioactive elements: the most stable isotope is very long-lived, with a half-life of over four million years.
  Significantly radioactive elements: the most stable isotope has half-life between 800 and 34,000 years.
  Radioactive elements: the most stable isotope has half-life between one day and 103 years.
  Highly radioactive elements: the most stable isotope has half-life between several minutes and one day.
  Extremely radioactive elements: the most stable isotope has half-life less than several minutes.

Of the elements with atomic numbers 1 to 92, all can be found in nature, having stable (such as hydrogen), or very long half-life (such as uranium) isotopes, or are created as common products of the decay of uranium and thorium (such as radon) — only technetium, of the elements below uranium, was man-made for its discovery in 1936.

All of the elements with higher atomic numbers, however, have been first discovered in the laboratory, with neptunium, plutonium, americium, curium, berkelium and californium later also discovered in nature. They are all radioactive, with a half-life much shorter than the age of the Earth, so any atoms of these elements, if they ever were present at the Earth's formation, have long since decayed. Trace amounts of these six elements form in some uranium-rich rock, and small amounts are produced during atmospheric tests of atomic weapons. The Np, Pu, Am, Cm, Bk, and Cf are generated from neutron capture in uranium ore with subsequent beta decays (e.g. 238U + n239U239Np239Pu).

Transuranic elements can be artificially generated synthetic elements, via nuclear reactors or particle accelerators. The half lives of these elements show a general trend of decreasing as atomic numbers increase. There are exceptions, however, including dubnium and several isotopes of curium. Further anomalous elements in this series have been predicted by Glenn T. Seaborg, and are categorised as the “island of stability.”[1]

Heavy transuranic elements are difficult and expensive to produce, and their prices increase rapidly with atomic number. As of 2008, weapons-grade plutonium cost around $4,000/gram,[2] and californium cost $60,000,000/gram.[3] Due to production difficulties, none of the elements beyond californium have industrial applications,[citation needed] and of them, only einsteinium has ever been produced in macroscopic quantities.[4]

Transuranic elements that have not been discovered, or have been discovered but are not yet officially named, use IUPAC's systematic element names. The naming of transuranic elements may be a source of controversy.

Discovery and naming of transuranium elements[edit]

So far, essentially all the transuranium elements have been produced at three laboratories:

The temporary names listed above are generic names assigned according to a convention (the systematic element names). They will be replaced by permanent names as the elements are confirmed by independent work.

List of the transuranic elements by chemical series[edit]

*The existence of these elements has been claimed and generally accepted, but not yet acknowledged by the IUPAC.

The names and symbols of elements 113, 115, 117, and 118 are provisional until permanent names for the elements are decided on, usually within a year after the discovery acknowledgement by IUPAC.

Super-heavy elements[edit]

Position of the transactinide elements in the periodic table.

Super-heavy elements, (also known as super heavy atoms, commonly abbreviated SHE) may refer to elements beyond atomic number 100, but also may refer to all transuranium elements. The transactinide elements begin with rutherfordium (atomic number 104).[5] They have only been made artificially, and currently serve no practical purpose because their short half-lives cause them to decay after a very short time, ranging from a few minutes to just a few milliseconds (except for dubnium, which has a half life of over a day), which also makes them extremely hard to study.[6][7]

Super-heavy atoms have all been created during the latter half of the 20th century and are continually being created during the 21st century as technology advances. They are created through the bombardment of elements in a particle accelerator. For example, the nuclear fusion of californium-249 and carbon-12 creates rutherfordium. These elements are created in quantities on the atomic scale and no method of mass creation has been found.[6]

See also[edit]

References[edit]

  1. ^ Considine, Glenn, ed. (2002). Van Nostrand's Scientific Encyclopedia (9th ed.). New York: Wiley Interscience. p. 738. ISBN 0-471-33230-5. 
  2. ^ "Price of Plutonium". The Physics Factbook. 
  3. ^ Rodger C. Martin and Steven E. Kos. "Applications and Availability of Californium-252 Neutron Sources for Waste Characterization" (pdf). 
  4. ^ Haire, Richard G. (2006). "Fermium, Mendelevium, Nobelium and Lawrencium". In Morss; Edelstein, Norman M.; Fuger, Jean. The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Dordrecht, The Netherlands: Springer Science+Business Media. ISBN 1-4020-3555-1. 
  5. ^ Uzi Kaldor; Stephen Wilson (2003). Theoretical chemistry and physics of heavy and superheavy elements. Springer. pp. 5, 8. ISBN 978-1-4020-1371-3. Retrieved 10 June 2011. 
  6. ^ a b Heenen, P. H.; Nazarewicz, W. (2002). "Quest for superheavy nuclei". Europhysics News 33: 5. Bibcode:2002ENews..33....5H. doi:10.1051/epn:2002102. 
  7. ^ Greenwood, N. N. (1997). "Recent developments concerning the discovery of elements 100–111". Pure and Applied Chemistry 69: 179. doi:10.1351/pac199769010179. 

Further reading[edit]