Sources/Uses
Most electropositive element with 1 natural isotope and no stable nuclides; Found in uranium minerals; [Merck Index] "Francium is a chemical element with symbol Fr and atomic number 87. . . . Francium is a highly radioactive metal that decays into astatine, radium, and radon. As an alkali metal, it has one valence electron. Bulk francium has never been viewed. Because of the general appearance of the other elements in its periodic table column, it is assumed that francium would appear as a highly reflective metal, if enough could be collected together to be viewed as a bulk solid or liquid. However preparing such a sample is impossible, since the extreme heat of decay (the half-life of its longest-lived isotope is only 22 minutes) would immediately vaporize any viewable quantity of the element." [Wikipedia]