On February 9, 1950, S. G. Thompson, A. Ghiorso, K. Street and G. T. Seaborg performed a careful ion exchange separation of the products formed by irradiation of microgram amounts of Cm 242 with 35 MeV helium ions produced by the 60-inch cyclotron at the University of California, Berkeley. A new radioactive isotope was found, which eluted just ahead of berkelium, in the position expected for element 98. This activity, was assigned to an isotope with mass number 245. The new element was named californium for the state in which it was discovered.