a radioactive, metallic chemical element, one of the actinides, produced by the beta decay of an isotope of plutonium: symbol, Am; at. no. 95
Origin of americiumModL, after Americ(a) + -ium: so named by G. T. Seaborg, one of its discoverers, by analogy with europium, the corresponding rare earth
A white metallic transuranic element of the actinide series, having isotopes with mass numbers from 232 to 247. Am-241 and Am-243 are the isotopes with the longest half-lifes (432.2 years and 7,370 years, respectively), and are alpha-ray and gamma-ray emitters used as radiation sources in research, radiography, and smoke alarms. Atomic number 95; melting point 1176°C; boiling point 2011°C; specific gravity 12; valence 3, 4, 5, 6. See Periodic Table.
Origin of americiumAfter America
- The chemical element (symbol Am) with an atomic number of 95.
From Americ(as) + -ium, by analogy with europium.