Francium, a chemical element with the properties of an alkali metal. It occurs only in radioactive forms, produced in nature by the disintegration of actinium. The most stable isotope has a half life of only 21 minutes. Francium has no commercial use. It was discovered by Marguerite Perey of the Curie Institute, Paris, in 1939.

Symbol: Fr. Atomic number: 87. Atomic weight (of most stable isotope): 223. Melting point: 80.6 (?) F. (27 [?] C.). Valence: +1. Francium appears just below cesium in the first group (IA) of the Periodic Table.