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n. Symbol Ac
A radioactive element found in uranium ores, used in equilibrium with its decay products as a source of alpha rays. Its longest lived isotope is Ac-227 with a half-life of 21.77 years. Atomic number 89; melting point 1,050°C; boiling point 3,198°C; specific gravity (calculated) 10.07; valence 3. See Periodic Table.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
(Elements & Compounds) 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,227Ac: 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 and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
ac•tin•i•um(ækˈtɪn i əm)
a radioactive, silver-white, metallic element that glows blue in the dark, resembling the rare earths in chemical behavior and valence. Symbol: Ac; at. no.: 89; at. wt.: 227.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
Symbol 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. Its most stable isotope has a half-life of about 22 years. Atomic number 89. See Periodic Table.
The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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|Noun||1.||actinium - a radioactive element of the actinide series; found in uranium ores|
chemical element, element - any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter
uranium ore - any ore from which uranium can be extracted
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
actinium[ækˈtɪnɪəm] N → actinio m
Collins Spanish Dictionary - Complete and Unabridged 8th Edition 2005 © William Collins Sons & Co. Ltd. 1971, 1988 © HarperCollins Publishers 1992, 1993, 1996, 1997, 2000, 2003, 2005