Fr
Francium
Atomic number: 87Mass: 223 uCategory: Alkali Metal
About Francium
Francium is an alkali metal and the second rarest naturally occurring element. It is extremely radioactive; its most stable isotope has a half-life of only 22 minutes. At any time, there is less than 30 grams of francium on Earth.
Properties
Period
7
Group
1
Block
S
Category
Alkali Metal
Electronegativity
0.70 (Pauling)
Ionization Energy
380 kJ/mol
Melting Point
281 K (8°C)
Boiling Point
950 K (677°C)
Density
1.87 g/cm³
Oxidation States
+1
Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 7s¹
[Rn] 7s¹
Shell 1:2e⁻
Shell 2:8e⁻
Shell 3:18e⁻
Shell 4:32e⁻
Shell 5:18e⁻
Shell 6:8e⁻
Shell 7:1e⁻
Real-World Uses
Research only
Nuclear chemistry studies
Atomic structure research
Fundamental physics
No commercial uses
Fun Fact
Francium is so radioactive and short-lived that the largest amount ever assembled in a lab was just 300,000 atoms — less than you can see with any microscope!