|
|
| General |
| Name, Symbol, Number |
berkelium, Bk, 97 |
| Chemical series |
actinides |
| Group, Period, Block |
n/a, 7, f |
| Appearance |
unknown, probably silvery
white or metallic gray |
| Atomic mass |
(247) g/mol |
| 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/cm³ |
| Density (near r.t.) |
(beta) 13.25 g/cm³ |
| Melting point |
(beta) 1259 K
(986 °C, 1807 °F) |
| Atomic properties |
| Electronegativity |
1.3 (Pauling scale) |
| Ionization energies |
1st: 601 kJ/mol |
| Miscellaneous |
| Magnetic ordering |
no data |
| Thermal conductivity |
(300 K) 10 W/(m·K) |
| CAS registry number |
7440-40-6 |
| Notable isotopes |
|
|
| References |
Berkelium 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. Berkelium was the fifth transuranic element to be synthesized.
Notable characteristics
Weighable amounts of berkelium-249 (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 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. 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 americium-241 with alpha particles to produce berkelium-243 (half-life 4.5 hours) and two free neutrons. One of the longest lived isotopes of the element, berkelium-249 (half-life 320 days), was later synthesized by subjecting a curium-244 target with an intense beam of neutrons.
Isotopes
19 radioisotopes of berkelium have been characterized, with the most stable being Bk-247 with a half-life of 1380 years, Bk-248 with a half-life of >9 years, and Bk-249 with a half-life of 320 days. All of the remaining radioactive isotopes have half-lifes that are less than 5 days, and the majority of these have half lifes that are less than 5 hours. This element also has 2 meta states, with the most stable being Bk-248m (t½ 23.7 hours). The isotopes of berkelium range in atomic weight from 235.057 amu (Bk-235) to 254.091 amu (Bk-254).
References
External links
|
