Berkelium is a transuranic radioactive chemical element with symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the University of California Radiation Laboratory where it was discovered in December 1949.
It took 250 days to make enough berkelium, shown here (in dissolved state), to synthesize element 117 - ORNL, Department of Energy, Public domain, via Wikimedia Commons