87
Fr
Francium
223
Francium (Fr)
Alkali MetalGroup 1Period 7s-block-blockRadioactive
Francium is a chemical element with symbol Fr and atomic number 87. It used to be known as eka-caesium and actinium K. It is the second-least electronegative element, behind only caesium. Francium is a highly radioactive metal that decays into astatine, radium, and radon.
Latin name: Francium
Atomic Number
87
Atomic Mass
223 g/mol
Phase (STP)
Solid (predicted)
Electron Config.
[Rn] 7s¹
General
SymbolFr
Atomic Number87
Atomic Mass223 g/mol
CategoryAlkali Metal
Group1
Period7
Blocks-block
Electron Configuration[Rn] 7s¹
Valence Electrons1
Colourunknown (predicted silvery metallic)
Physical Properties
Phase (STP)Solid (predicted)
Atomic Properties
Atomic Radius348 pm
Electronegativity0.7 Pauling
Ionization Energy380 kJ/mol
Oxidation States+1
Ion ChargeFr+
Nuclear & Hazards
RadioactiveYes
Half-life22 minutes (Fr-223, typical longest-lived isotope)
Abundance
In Universe0.00000000000001%
In Earth's Crust0.00000000000001%
Discovery & History
Discovery Year1939
Discovered ByMarguerite Perey
Country of DiscoveryFrance
Isotopes of Francium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Fr-221 | — | 4.9 minutes | α, β⁻ |
| Fr-223 | — | 22.0 minutes | β⁻, α |