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francium

[fran-see-uh m] /ˈfræn si əm/
noun, Chemistry
1.
a radioactive element of the alkali metal group. Symbol: Fr; atomic number: 87.
Origin
1945-1950
1945-50; after France where first identified; see -ium
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Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for francium

francium

/ˈfrænsɪəm/
noun
1.
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
Word Origin
C20: from New Latin, from France + -ium; so-called because first found in France
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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francium in Medicine

francium fran·ci·um (frān'sē-əm)
n.
Symbol Fr
An extremely unstable radioactive element of the alkali metals, having [approx] 19 isotopes, the most stable of which is Fr 223 with a half-life of 21 minutes. Atomic number 87; valence 1.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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francium in Science
francium
  (frān'sē-əm)   
Symbol Fr
An extremely unstable, radioactive element of the alkali group. It is the heaviest metal of the group. Francium occurs in nature, but less than 28.35 g (1 oz) is present in the Earth's crust at any time. It has approximately 19 isotopes, the most stable of which is Fr 223 with a half-life of 21 minutes. Atomic number 87; valence 1. See Periodic Table.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Article for francium

Fr

heaviest chemical element of Group 1 (also called Group Ia) in the periodic table, the alkali metal group. It exists only in short-lived radioactive forms. Natural francium cannot be isolated in visible, weighable amounts, for only about 30 grams (about 1 ounce) occur at any time in the entire crust of Earth. Marguerite Perey discovered francium (1939) while studying actinium-227, which decays by negative beta decay (electron emission) to an isotope of thorium (thorium-227) and by alpha emission (about 1 percent) into an isotope of francium (francium-223) that was formerly called actinium K (AcK) and is a member of the actinium decay series. Though it is the longest-lived isotope of francium, francium-223 has a half-life of only 21 minutes. Isotopes of francium with masses between 204 and 224 have been artificially prepared, and, because natural francium cannot be concentrated, it is also prepared by neutron irradiation of radium to produce actinium, which decays to produce traces of francium. The chemistry of francium can be studied only by methods designed for trace quantities. In all respects, its observed behaviour, including the oxidation state of +1, is that to be expected of an alkali element filling a place just below cesium in the periodic table of the elements

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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