americium

[am-uh-rish-ee-uhm]
noun Chemistry.
a transuranic element, one of the products of high-energy helium bombardment of uranium and plutonium. Symbol: Am; atomic number: 95.

Origin:
1945–50, Americanism; Americ(a) + -ium

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World English Dictionary
americium (ˌæməˈrɪsɪəm)
 
n
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)
 
[C20: from America (because it was discovered at Berkeley, California) + -ium]

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Medical Dictionary

americium am·er·i·ci·um (ām'ə-rĭsh'ē-əm)
n.
Symbol Am
A white metallic synthetic element of the actinide series; its longest-lived isotopes, Am 241 and Am 243, are used as radiation sources in research. Atomic number 95; specific gravity 13.7; valence 2, 3, 4, 5, 6.

The American Heritage® Stedman's Medical Dictionary
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Science Dictionary
americium   (ām'ə-rĭsh'ē-əm)  Pronunciation Key 
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.
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Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Example sentences
The primary plutonium decay products are isotopes of uranium, neptunium, and americium.
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