francium(redirected from eka-caesium)
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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.
(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]
fran•ci•um(ˈfræn si əm)
a radioactive element of the alkali metal group. Symbol: Fr; at. no.: 87.
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.
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|Noun||1.||francium - a radioactive element of the alkali-metal group discovered as a disintegration product of actinium|