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5 definitions found

From: DICT.TW English-Chinese Dictionary 英漢字典

 ac·tin·i·um /ækˈtɪniəm/

From: DICT.TW English-Chinese Medical Dictionary 英漢醫學字典

 ac·tin·i·um /ækˈtɪnɪəm/ 名詞

From: Webster's Revised Unabridged Dictionary (1913)

 Ac·tin·i·um n.  Chem. A supposed metal, said by Phipson to be contained in commercial zinc; -- so called because certain of its compounds are darkened by exposure to light.

From: WordNet (r) 2.0

      n : a radioactive element of the actinide series; found in
          uranium ores [syn: Ac, atomic number 89]

From: Elements database 20001107

 Symbol: Ac
 Atomic number: 89
 Atomic weight: (227)
 Silvery radioactive metallic element, belongs to group 3 of the periodic
 table. The most stable isotope, Ac-227, has a half-life of 217 years.
 Ac-228 (half-life of 6.13 hours) also occurs in nature. There are 22 other
 artificial isotopes, all radioactive and having very short half-lives.
 Chemistry similar to lanthanum. Used as a source of alpha particles.
 Discovered by A. Debierne in 1899.