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
Origin of promethiumModL: so named (1949) for earlier prometheum, name proposed by G. M. Coryell, wife of one of the discoverers ; from Classical Greek Prom?theus (see Prometheus) in reference to production by nuclear fission + -ium
A radioactive rare-earth element prepared by fission of uranium or by neutron bombardment of neodymium, having nearly 50 isotopes and isomers, of which the most stable have half-lives of 2.62 years (Pm-147), 5.53 years (Pm-146), and 17.7 years (Pm-145). Promethium-147 is most easily obtained and is used as a source of beta rays. Atomic number 61; melting point 1,042°C; boiling point 3000°C; specific gravity 7.264 (25°C); valence 3. See Periodic Table.
Origin of promethiumFrom Prometheus.
- A metallic chemical element (symbol Pm) with an atomic number of 61.