'promethium' definitions:
Definition of 'promethium'
(from WordNet)
noun
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]
Definition of 'promethium'
From: Elements
- 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.