Berkelium

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MELTING POINT: 986°C
BOILING POINT : Unknown
DENSITY : Unknown
MOST COMMON IONS : Bk ³⁺ , Bk ⁴⁺

Berkelium, element 97, is a synthetic radioelement , first synthesized by Glenn Seaborg's group in 1949. A target of a few milligrams of an isotope of americium ( ²⁴¹ Am) was bombarded with α -particles within a cyclotron at the University of California at Berkeley. An α -emitting species with a half-life of 4.5 hours was isolated via ion exchange chromatography and identified as being an isotope of element 97 with mass number 243. The first isolation of a berkelium compound was accomplished by Stanley Thompson and B. B. Cunningham in 1958. The known isotopes of berkelium have mass numbers that range from 240 to 251, and are all radioactive. The longest-lived isotope has a mass number of 247 and a half-life of 1,380 years. The ground state electronic configuration of the outer orbitals of berkelium is 5 f ⁸ 6 d ¹ 7 s ² . In compounds and in aqueous solution , berkelium is present in oxidation states III (the more stable) and IV.

Berkelium was named for the city in which it was discovered, in part to emphasize its relationship to its analog in the lanthanide series, terbium, which was named for the city of Ytterby in Sweden (where many of the rare earth minerals had been discovered). Metallic berkelium has a face-centered cubic structure—something it has in common with the actinide elements americium though einsteinium. Due to the very high level of radioactivity of even the long-lived isotopes, berkelium is usually studied at tracer level concentrations. The most commonly studied isotope is ²⁴⁹ Bk, with a half-life of 320 days. This nuclide has been isolated at milligram levels and undergoes β -decay.

SEE ALSO Actinium ; Einsteinium ; Fermium ; Lawrencium ; Mendelevium ; Neptunium ; Nobelium ; Plutonium ; Protactinium ; Rutherfordium ; Seaborg, Glenn Theodore ; Thorium ; Uranium .

Gregory R. Choppin

Bibliography

Choppin, Gregory R.; Liljenzin, Jan-Olov; and Rydberg, Jan (2001). Radiochemistry and Nuclear Chemistry , 3rd edition. Woburn, MA: Butterworth-Heinemann.

Seaborg, Glenn T., and Loveland, Walter D. (1990). The Elements Beyond Uranium. New York: Wiley-Interscience.