2 definitions found From WordNet (r) 2.0 [wn]: francium noun: a radioactive element of the alkali-metal group discovered as a disintegration product of actinium [syn: {Fr}, {atomic number 87}] From Elements database 20001107 [elements]: francium Symbol: Fr Atomic number: 87 Atomic weight: (223) Radioactive element, belongs to group 1 of the periodic table. Found in uranium and thorium ores. The 22 known isotopes are all radioactive, with the most stable being Fr-223. Its existence was confirmed in 1939 by Marguerite Perey.

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