Berkelium

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Bk redirects here. For other uses of the abbreviation, see BK.
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Tb

Bk

(Uqs)
General
Name, Symbol, Number berkelium, Bk, 97
Chemical series Actinide
Group, Period, Block n/a, 7, f
Appearance unknown, probably silvery
white or metallic gray
Standard atomic weight (247)  g·mol−1
Electron configuration [Rn] 5f9 7s2
Electrons per shell 2, 8, 18, 32, 27, 8, 2
Physical properties
Phase solid
Density (near r.t.) (alpha) 14.78  g·cm−3
Density (near r.t.) (beta) 13.25  g·cm−3
Melting point (beta) 1259 K
(986 °C, 1807 °F)
Atomic properties
Oxidation states 3, 4
Electronegativity 1.3 (scale Pauling)
Ionization energies 1st: 601 kJ/mol
Miscellaneous
Crystal structure hexagonal close-packed
Magnetic ordering no data
Thermal conductivity (300 K) 10  W·m−1·K−1
CAS registry number 7440-40-6
Selected isotopes
Main article: Isotopes of berkelium
iso NA half-life DM DE (MeV) DP
245Bk syn 4.94 d ε 0.810 245Cm
α 6.455 241Am
246Bk syn 1.8 d α 6.070 242Am
ε 1.350 246Cm
247Bk syn 1380 y α 5.889 243Am
248Bk syn >9 y α 5.803 244Am
249Bk syn 330 d α 5.526 245Am
SF - -
β- 0.125 249Cf
References

Berkelium (IPA: /bəˈkiːliəm/) is a synthetic element in the periodic table that has 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 Berkeley, California and the University of California, Berkeley. Berkelium was the fifth transuranic element to be synthesized.

Contents

[edit] 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 acids.

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.[citation needed] This element has no known uses outside of basic research and plays no biological role.

[edit] 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.

[edit] 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).

[edit] References

[edit] External links

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