prot·ac·tin·i·um /ˌproˌtækˈtɪniəm/
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prot·ac·tin·i·um /ˌproto-/ 名詞
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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]
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.