Berkelium

"Bk redirects here. For other uses of the abbreviation, see BK (disambiguation)."Berkelium (pronEng|bɚˈkiːliəm or IPA|/ˈbɝkliəm/ Fact|date=March 2008) is a synthetic element with the symbol Bk and atomic number 97. A radioactive metallic element in the actinide series, berkelium was first synthesized by bombarding americium with alpha particles (helium ions) and was named after the University of California, Berkeley. Berkelium was the fifth transuranic element to be synthesized.

Notable characteristics

Weighable amounts of 249Bk (half-life 314 days) make it possible to determine some of its properties using macroscopic quantities. As of 2004 it had not been isolated in its elemental form, but it is predicted to be a silvery metal that would easily oxidize in air at elevated temperatures and would be soluble in dilute mineral acidsFact|date=May 2008.

X-ray diffraction techniques have been used to identify various berkelium compounds such as berkelium dioxide (BkO2), berkelium fluoride (BkF3), berkelium oxychloride (BkOCl), and berkelium trioxide (BkO3). In 1962 visible amounts of berkelium chloride (BkCl3) were isolated that weighed 3 billionths of a gram. This was the first time visible amounts of a pure berkelium compound were produced.

Like other actinides, berkelium bio-accumulates in skeletal tissue.Fact|date=February 2007 This element has no known uses outside of basic research and plays no biological role.

History

Berkelium was first synthesized by Glenn T. Seaborg, Albert Ghiorso, Stanley G. Thompson, and Kenneth Street, Jr at the University of California, Berkeley in December 1949. The team used a cyclotron to bombard a milligram-sized target of 241Am with alpha particles to produce 243Bk (half-life 4.5 hours) and two free neutrons. One of the longest lived isotopes of the element, 249Bk (half-life 330 days), was later synthesized by subjecting a 244Cm target with an intense beam of neutrons.

Isotopes

19 radioisotopes of berkelium have been characterized, with the most stable being 247Bk with a half-life of 1380 years, 248Bk with a half-life of >9 years, and 249Bk with a half-life of 330 days. All of the remaining radioactive isotopes have half-lives that are less than 5 days, and the majority of these have half-lives that are less than 5 hours. This element also has 2 meta states, with the most stable being 248mBk (t½ 23.7 hours). The isotopes of berkelium range in atomic weight from 235.057 u (235Bk) to 254.091 u (254Bk).

Nuclear fuel cycle

In the nuclear fuel cycle, berkelium is produced by beta decay of curium. The first curium isotope to undergo beta decay is Cm-249 with a halflife of just over an hour, so Bk-249 is the only isotope of berkelium produced in significant quantities in nuclear reactors. Production of Bk-249 requires 11 successive neutron captures on uranium-238 without nuclear fission or alpha decay, so it is only produced in small amounts.

249Bk has a moderately large neutron capture cross section of 710 barns for thermal neutrons, 1200 barns resonance integral, but very low fission cross section for thermal neutrons. If still in a thermal reactor, much of it will therefore be converted to 250Bk which quickly decays to californium-250, but some alpha decays to curium-245.

References

* [http://periodic.lanl.gov/elements/97.html Los Alamos National Laboratory - Berkelium]
* [http://education.jlab.org/itselemental/ele097.html It's Elemental - Berkelium]
* [http://sciencereview.berkeley.edu/articles.php?issue=1&article=elementary Berkeley Science Review - An Elementary Problem]

External links

* [http://www.webelements.com/webelements/elements/text/Bk/index.html WebElements.com - Berkelium]


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  • berkelium — er*ke li*um (b[ e]r*k[=e] l[ e]*[u^]m), n. [from the city of Berkeley, California, location of the University of California campus where it was discovered.] a chemical element of the transuranic series. Chemical symbol Bk; atomic number 97;… …   The Collaborative International Dictionary of English

  • berkelium — BERKÉLIUM s.n. v. berkeliu. Trimis de LauraGellner, 13.09.2007. Sursa: DN …   Dicționar Român

  • berkelium — Symbol: Bk Atomic number: 97 Atomic weight: (247) Radioactive metallic transuranic element. Belongs to actinoid series. Eight known isotopes, the most common Bk 247, has a half life of 1.4*10^3 years. First produced by Glenn T. Seaborg and… …   Elements of periodic system

  • berkelium — ☆ berkelium [bʉrk′lē əm ] n. [ModL, after BERKELEY2, Calif. + IUM: so named by Glenn T. Seaborg, U.S. chemist and one of its discoverers, by analogy with TERBIUM] a radioactive, metallic chemical element, one of the actinides, initially produced… …   English World dictionary

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  • berkelium — /beuhr kee lee euhm/, n. Chem. a transuranic element. Symbol: Bk; at. no.: 97; at. wt.: 249 (?). [1945 50; named after BERKELEY, California, where it was discovered; see IUM] * * * ▪ chemical element  (Bk),    synthetic chemical element of the… …   Universalium

  • Berkelium — Ber|ke|li|um 〈n.; s; unz.; Chem.; 〉 künstl. hergestelltes radioaktives chem. Element, Ordnungszahl 97 [nach der Stadt Berkeley in Kalifornien] * * * Ber|ke|li|um [nach dem Ort der erstmaligen Herst. Berkeley (California, USA); ↑ ium (1)], das; s; …   Universal-Lexikon

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