Transuranic element

Transuranic element

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

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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).

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 generated are from neutron capture in uranium ore with subsequent beta decays (e.g. 238U + n239U239Np239Pu).

Those that can be found on Earth now are 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 go up 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 has industrial applications, 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

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

*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


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 are beginning 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

References

Further reading

  • Eric Scerri, A Very Short Introduction to the Periodic Table, Oxford University Press, Oxford, 2011.
  • The Superheavy Elements
  • Annotated bibliography for the transuranic elements from the Alsos Digital Library for Nuclear Issues.
  • Transuranium elements
  • Super Heavy Elements network official website (network of the European integrated infrastructure initiative EURONS)
  • Darmstadium and beyond
  • Christian Schnier, Joachim Feuerborn, Bong-Jun Lee: Traces of transuranium elements in terrestrial minerals? (Online, PDF-Datei, 493 kB)
  • Christian Schnier, Joachim Feuerborn, Bong-Jun Lee: The search for super heavy elements (SHE) in terrestrial minerals using XRF with high energy synchrotron radiation. (Online, PDF-Datei, 446 kB)


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