Intensely radioactive and 150 times more so than radium — actinium glows pale blue in the dark.
- Atomic number
- 89
- Atomic mass
- 227 u
- Phase
- Solid
- Electron configuration
- [Rn] 6d¹ 7s²
- Melting point
- 1,323 K · 1,049.9 °C
- Boiling point
- 3,471 K · 3,197.9 °C
- Density
- 10.07 g/cm³
- Electronegativity
- 1.1
- Period / Group
- 7 / —
- Discovery year
- 1899