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promethium |
2 definitions found From WordNet r 1.6 [wn]: promethium n : a soft silvery metallic element of the rare earth group having no stable isotope; was discovered in radioactive form as a fission product of uranium [syn: {Pm}, {atomic number 61}] From Elements database 20001107 [elements]: promethium Symbol: Pm Atomic number: 61 Atomic weight: (147) Soft silvery metallic element, belongs to the lanthanoids. Pm-147, the only natural isotope, is radioactive and has a half-life of 252 years. Eighteen radioisotopes have been produced, but all have very short half-lives. Found only in nuclear decay waste. Pm-147 is of interest as a beta-decay source, however Pm-146 and Pm-148 have to be removed from it first as they generate gamma radiation. Discovered by J.A. Marinsky L.E. Glendenin and C.D. Coryell in 1947.
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