The second rarest natural element, and one of the most electropositive — but no one has ever seen a visible sample.
- Atomic number
- 87
- Atomic mass
- 223 u
- Phase
- Solid
- Electron configuration
- [Rn] 7s¹
- Melting point
- 300 K · 26.9 °C
- Boiling point
- 950 K · 676.9 °C
- Density
- 1.87 g/cm³
- Electronegativity
- 0.7
- Period / Group
- 7 / 1
- Discovery year
- 1939