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definitions

actinium

[ak-tin-ee-uh m]
noun Chemistry.
  1. 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.

Origin of actinium

First recorded in 1900–05; actin- + -ium
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for actinium

Historical Examples of actinium

  • Actinium, an element or elementary substance obtained in minute quantities in connection with the study of radioactivity.

  • In 1902 Giesel discovered another substance which he called emanium, and which was considered to be identical with actinium.

  • Uranium certainly is; thorium—the stuff of this incandescent gas mantle—certainly is; actinium.

    The World Set Free

    Herbert George Wells

  • M. Debierne has obtained a third radioactive substance from pitchblende, which he has called “Actinium.”

    Alchemy: Ancient and Modern

    H. Stanley Redgrove

  • Other radio-active substances have each several derivatives: actinium has nine, uranium has four.

British Dictionary definitions for actinium

actinium

noun
  1. 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 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for actinium
n.

radioactive element discovered in 1899, from Greek actin-, comb. form of aktis (genitive aktinos) "ray, radiance" (see actino-) + chemical suffix -ium.

Online Etymology Dictionary, © 2010 Douglas Harper
actinium in Medicine

actinium

[ăk-tĭn′ē-əm]
n. Symbol Ac
  1. 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.
actinium in Science

actinium

[ăk-tĭn′ē-əm]
Ac
  1. 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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.