Search Result for "promethium": 
Wordnet 3.0

NOUN (1)

1. 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: promethium, Pm, atomic number 61]


WordNet (r) 3.0 (2006):

promethium n 1: 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: promethium, Pm, atomic number 61]
The Elements (07Nov00):

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.