Berkelium

Berkelium, symbol Bk, artificially created radioactive metallic element. The atomic number of berkelium is 97; the element is one of the transuranium elements in the actinide series of the periodic table (see Periodic Law). Berkelium was discovered in 1949 by the American chemists Glenn T. Seaborg, Stanley G. Thompson, and Albert Ghiorso at the University of California laboratories in Berkeley, California, for which the element was named. An isotope of mass number 243 with a half-life of 4.6 hours was produced by bombarding americium-241 with alpha particles accelerated in a cyclotron (see Particle Accelerators). Several other isotopes have subsequently been produced. The most stable isotope of berkelium, with a half-life of about 1,400 years, has a mass number of 247. See also Radioactivity.