- 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
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Examples from the Web for 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.Inventors at Work
- 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
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
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
- 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.
- 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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