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De - Pt| English Dictionary: Actinium | by the DICT Development Group |
| 3 results for Actinium | |
| From WordNet (r) 3.0 (2006) [wn]: | |
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| From Webster's Revised Unabridged Dictionary (1913) [web1913]: | |
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Actinium \Ac*tin"i*um\, n. [Gr. [?], [?], ray.] (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 The Elements (22Oct97) [elements]: | |
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actinium 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. | |
