am·er·i·ci·um ( m  -r sh  -m)n. Symbol Am A white metallic transuranic element of the actinide series, having isotopes with mass numbers from 237 to 246 and half-lives from 25 minutes to 7,950 years. Its longest-lived isotopes, Am 241 and Am 243, are alpha-ray emitters used as radiation sources in research. Atomic number 95; specific gravity 11.7; valence 3, 4, 5, 6. See Table at element. [After America.] |
americium [ˌæməˈrɪsɪəm]
n
(Chemistry / Elements & Compounds) a white metallic transuranic element artificially produced from plutonium. It is used as an alpha-particle source. Symbol: Am; atomic no.: 95; half-life of most stable isotope, 243Am: 7.4 ✕ 103 years; valency: 2,3,4,5, or 6; relative density: 13.67; melting pt.: 1176°C; boiling pt.: 2607°C (est.)
[from America (because it was discovered at Berkeley, California) + -ium]
| americium (m-rsh-m) Symbol Am A synthetic, silvery-white, radioactive metallic element of the actinide series that is produced artificially by bombarding plutonium with neutrons. Americium is used as a source of alpha particles for smoke detectors and gamma rays for industrial gauges. Its most stable isotope has a half-life of 7,950 years. Atomic number 95; specific gravity 11.7; valence 3, 4, 5, 6. See Periodic Table. |
ThesaurusLegend: Synonyms Related Words Antonyms
| Noun | 1. |  americium - a radioactive transuranic metallic element; discovered by bombarding uranium with helium atomsmetal, metallic element - any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc. |
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