franciumn.
/ˈfransɪəm/, /ˈfrɑːnsɪəm/, U.S. /ˈfræn(t)siəm/ Chemistry.
A very rare, unstable, radioactive metallic element, atomic number 87, which is the heaviest member of the alkali-metal series and is chemically similar to caesium. Symbol Fr.All the isotopes of francium have short half-lives and only one, francium-223, occurs naturally (half-life 22 minutes), being produced by the radioactive decay of actinium-227 in uranium and thorium ores, and decaying itself into radon-223 and astatine-219. It is used principally in investigations of atomic energy levels and coupling constants.
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virginium1932
francium1946
1946 Jrnl. & Proc. Royal Inst. Chem. Dec. 277 For element 87,..the name Francium (Fr) has been suggested.
1951 J. R. Partington Gen. & Inorg. Chem. (ed. 2) xii. 323A It was at first called actinium-K but has been renamed francium (Fr.).
1963 A. G. Maddock in Mellor's Compreh. Treat. Inorg. & Theor. Chem. II. 3rd Suppl. ii. vi. 2518 Asimov has calculated that the earth's crust contains 24·5 g. of francium.
1968 C. A. Hampel Encycl. Chem. Elem. 224/1 Francium exists in aqueous solution as a large singly-charged ion with small tendency to form complex ions.
2002 L. Orozco in S. N. Atutov et al. Trapped Particles & Fund. Physics 126 It is now possible to perform precise measurements of the atomic properties of francium.
This entry has been updated (OED Third Edition, September 2009; most recently modified version published online March 2022).
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n.1946