Element Properties, Isotopic Compositions for Francium Francium (Fr) Element Properties Atomic Mass 223 Atomic Number 87 Name Origins Named after France Year Discovered 1939 Discovery Credits Discovered by Marguerite Perey in Paris, France. Remarks Intensely radioactive, short lived metal element. Primarily occurs as a trace amount (a few ppm) in uranium or thorium minerals where it is a decay product of uranium and/or thorium. References Emsley, J., 1991; THE ELEMENTS : Sec. Ed., Clarendon Press, Oxford, 251 p. See Also WebElements, ChemiCool Naturally Occurring Isotopes Symbol Isotope Mass Isotope Nuclide Number Isotope Number Natural Abundance Half-life Half-life Units Decay Mode Decay Mode MeV Decay Mode % Fr 211.99613 212 87 Trace 20 min. EC alpha 5.07 6.529 57.0% 43.0% Fr 223.019733 223 87 Trace 21.8 min. beta - 1.147 100.0% There are no minerals containing Francium (Fr)