francium (redirected from Actinium K)

francium (frăn`sēəm) [from France], radioactive chemical element; symbol Fr; at. no. 87; mass no. of most stable isotope 223; m.p. about 27°C; (estimated); b.p. 677°C; (estimated); sp. gr. unknown; valence +1. Francium is extremely rare; its most stable isotope (half-life about 22 minutes) occurs naturally, to a very limited extent, in uranium minerals. More than 30 other isotopes of francium are known; some are prepared by bombarding thorium with protons, deuterons, or alpha particles. Francium is one of the alkali metals found in Group 1 of the periodic table. Because it is so rare, its chemical and physical properties are not known, but it is believed to resemble cesium. The element was discovered in 1939 by Marguerite Perey at the Curie Institute in Paris as a product of the radioactive disintegration of actinium. In the United States it was at one time called virginium.

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francium

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

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francium [′fran·sē·əm]

(chemistry)

A radioactive alkali-metal element, symbol Fr, atomic number 87, atomic weight distinguished by nuclear instability; exists in short-lived radioactive forms, the chief isotope being francium-223.