francium(redirected from Actinium K)
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n. Symbol Fr
An extremely unstable radioactive element of the alkali metals, produced by alpha decay of actinium or artificially from thorium, having over 40 isotopes and isomers, the most stable of which is Fr-223 with a half-life of 22 minutes. Atomic number 87; melting point 27°C; boiling point 677°C; valence 1. 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) an unstable radioactive element of the alkali-metal group, occurring in minute amounts in uranium ores. Symbol: Fr; atomic no: 87; half-life of most stable isotope, 223Fr: 22 minutes; valency: 1; melting pt: 27°C; boiling pt: 677°C
[C20: from New Latin, from France + -ium; so-called because first found in France]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
fran•ci•um(ˈfræn si əm)
a radioactive element of the alkali metal group. Symbol: Fr; at. no.: 87.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
Symbol Fr An extremely unstable, radioactive element that is the heaviest alkali metal. Francium occurs in nature, but less than one ounce (30 grams) is present in the Earth's crust at any time. The most stable of its several isotopes has a half-life of 21 minutes. Atomic number 87. 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.||francium - a radioactive element of the alkali-metal group discovered as a disintegration product of actinium|
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