Berkelium
:
Bk redirects here. For other uses of the abbreviation, see
BK.
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 and the
University of California, Berkeley. Berkelium was the fifth
transuranic element to be synthesized.
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 (BkO
2), berkelium fluoride (BkF
3), berkelium oxychloride (BkOCl), and berkelium trioxide (BkO
3). 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.
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 320 days), was later synthesized by subjecting a
244Cm target with an intense beam of
neutrons.
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 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
248mBk (t
½ 23.7 hours). The isotopes of berkelium range in
atomic weight from 235.057
amu (
235Bk) to 254.091 amu (
254Bk).
*
Los Alamos National Laboratory - Berkelium*
It's Elemental - Berkelium*
WebElements.com - Berkelium
