Protactinium

3 definitions found

From The Collaborative International Dictionary of English v.0.48 [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]



From WordNet (r) 2.0 [wn]:

  protactinium
       n : a short-lived radioactive metallic element formed from
           uranium and disintegrating into actinium and then into
           lead [syn: {protoactinium}, {Pa}, {atomic number 91}]

From Elements database 20001107 [elements]:

  protactinium
  Symbol: Pa
  Atomic number: 91
  Atomic weight: (231)
  Radioactive metallic element, belongs to the actinoids. The most stable
  isotope, Pa-231 has a half-life of 2.43*10^4 years. At least 10 other
  radioactive isotopes are known. No practical applications are known.
  Discovered in 1917 by Lise Meitner and Otto Hahn.