protactinium
NounWordNet 3.0
Noun (1)
- a short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into leadSynonyms: protoactiniumPaatomic number 91
Webster's Dictionary (GCIDE)
Protactinium \Protactinium\ The radioactive chemical element, of atomic number 91; Atomic symbol Pa; at. wt. of longest-lived isotope, 231 (T1/2 = 32,500 yrs.) Also called brevium, Uranium X2 and UX2. [PJC]