Berkelium (IPA: /bəˈkiːliəm/) is a synthetic, radioactive, chemical element in the periodic table that has the symbol Bk and atomic number 97. It is a metallic element and part of the actinide series. Berkelium was invented by scientists and does not exist in nature. Berkelium was first made by hitting americium with alpha particles or helium ions. It is named after Berkeley, California and the University of California, Berkeley.