actinium
[ ak-tin-ee-uhm ]
/ ækˈtɪn i əm /
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noun Chemistry.
a radioactive silver-white metallic element that glows blue in the dark, resembling the rare earths in chemical behavior and valence. Symbol: Ac; atomic number: 89; atomic weight: 227.
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British Dictionary definitions for actinium
actinium
/ (ækˈtɪnɪəm) /
noun
a radioactive element of the actinide series, occurring as a decay product of uranium. It is used as an alpha-particle source and in neutron production. Symbol: Ac; atomic no: 89; half-life of most stable isotope, 227 Ac: 21.6 years; relative density: 10.07; melting pt: 1051°C; boiling pt: 3200 ± 300°C
Word Origin for actinium
C19: New Latin, from actino- + -ium
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
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Medical definitions for actinium
actinium
[ ăk-tĭn′ē-əm ]
n. Symbol Ac
A radioactive element found in uranium ores. Its longest lived isotope is Ac 227 with a half-life of 21.6 years. Atomic number 89.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Scientific definitions for actinium
actinium
[ ăk-tĭn′ē-əm ]
Ac
A silvery-white, highly radioactive metallic element of the actinide series that is found in uranium ores. It is about 150 times more radioactive than radium and is used as a source of alpha rays and neutrons. Its most stable isotope has a half-life of about 22 years. Atomic number 89; melting point 1,050°C (1,922°F); boiling point (estimated) 3,200°C (5,792°F); specific gravity (calculated) 10.07; valence 3. See Periodic Table.
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