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protactinium |
2 definitions found From WordNet r 1.6 [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.
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