Francium

Francium, chemical element, symbol Fr; for physical constants see Periodic Table. Francium was discovered by Marguerite Perey in 1939. It is found in uranium minerals and is formed by the decay of actinium. Francium can also be produced by bombarding thorium with protons. It is the heaviest member of the alkali metal series and the most unstable of the first 101 elements. The longest lived isotope, francium-223, has a half-life of 22 minutes.