Berkelium (IPA: /bəˈkiːliəm/) is a chemical element in the periodic table. Berkelium has the symbol Bk and atomic number 97. It is a radioactive metallic element and an actinide. 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.