Was discovered in radioactive form as a fission product of uranium

• A soft silvery metallic element of the rare earth group having no stable isotope

WordNet Word definitions in WordNet
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 ]

Wiktionary Word definitions in Wiktionary
n. A metallic chemical element (''symbol'' Pm) with an atomic number of 61.

Wikipedia Word definitions in Wikipedia
Promethium , originally prometheum , is a chemical element with the symbol Pm and atomic number 61. All of its isotopes are radioactive; it is one of only two such elements that are followed in the periodic table by elements with stable forms, a distinction ...

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
radioactive element, long one of the "missing elements," 1948, so called by discoverers Jacob Marinsky and Lawrence Glendenin, who detected it in 1945 in the fusion products of uranium while working on the Manhattan Project. From Prometheus , who stole ...