Francium is a chemical element with symbol Fr and atomic number 87. It was formerly known as eka-caesium and actinium K. It is one of the two least electronegative elements, the other being caesium. Francium is a highly radioactive metal that decays into astatine, radium, and radon. As an alkali metal, it has one valence electron.Symbol: Fr
Electron configuration: Rn 7s1
Atomic number: 87
Melting point: 27 °C
Discovered: 1939
Atomic mass: 223 u