promethium

noun

a radioactive chemical element, one of the rare-earth elements, obtained from fission of uranium or neutron bombardment of neodymium and used in phosphorescent paint, as a power source, X-ray source, etc.: symbol, Pm; at. no., 61

Etymology: ModL: so named (1949) for earlier prometheum, name proposed by G. M. Coryell for element isolated (1948) by J. A. Marinsky & L. E. Glendenin, U.S. physicists < Gr Promētheus (see Prometheus) in reference to production by nuclear fission + -ium