berkelium /(bẽr*kē"lē̇*ŭm)/

ber·ke·li·um

berkelium

n.
  1. a chemical element of the transuranic series. Chemical symbol Bk; atomic number 97; atomic weight 247. It is a radioactive element, with no stable isotopes; the longest-lived isotope is of mass number 247.07, decaying by alpha-emission with a half-life of 1,400 years. The isotope with atomic weight 249 has a half-life of 314 days, and was isolated in weighable quantities.