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

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 ]

Wikipedia Word definitions in Wikipedia
Promethium may refer to: Promethium , the chemical element A fictional petroleum-based fossil fuel as well as a refined napalm-like substance in Warhammer 40,000 Promethium, the name of the Mechanic Empire's queen in the fictional universe of Leiji Matsumoto ...

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 ...

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