Discovered | Name | Characteristics | Uses

The element is a member of the actinide series, which stretches from actinium (Ac) to lawrencium (Lr). Berkelium is a synthetic element; none occurs naturally on earth.

It is named for Berkeley, California, home of the University of California where the element was discovered in December, 1949 by S. G. Thompson, A. Ghiorso, and Seaborg. The symbol Bk is derived from the name. (Other logical symbols Be and Br had already been used for beryllium and bromine, respectively.) It was reasonable to name the element for the city in which it was discovered, as this was done previously for elements such as yttrium (Y), terbium (Tb), erbium (Er), and ytterbium (Yb), all named for the town of Ytterby in Sweden.

Chemical properties of berkelium have been studied mainly using trace amounts, since macroscopic quantities are difficult to isolate. Berkelium exists in aqueous solutions in two oxidation states, berkelium (III) and berkelium (IV). The chemistry and solubility of its compounds appears to closely follow the other transuranium elements.

Berkelium was the fifth transuranium element synthesized. It was produced by cyclotron bombardment of milligram amounts of 241Am with helium ions.

241Am + 4He 2 1n + 243Bk

The first isotope produced had a mass number of 243 and decayed by electron capture with a half-life of 4.5 hrs. Nine isotopes are now known. Of these, berkelium--249, with a half life of 320 days, can be produced in milligram quantities by neutron bombardment of curium--244.

244Cm + 5 1n 249Cm

249Cm 249Bk + b

The existence of 249Bk with a half-life of about 320 days makes it feasible to isolate berkelium in weighable amounts so that its properties can be investigated. One of the first visible amounts of a pure berkelium compound (berkelium chloride) was produced in 1962. It weighed about three billionths of a gram. The chloride, fluoride, sulfide, nitrate, sulfate, perchlorate, oxide, and dioxide have been produced, but none in large enough quantity to be commercially useful.