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Actinium (Ac)
Atomic number 89 · Actinide
| Atomic number | 89 |
|---|---|
| Atomic mass | 227.0 u |
| Molar mass | 227.0 g/mol |
| Category | Actinide |
| Group / period / block | 3 / 7 / d |
| Electron configuration | [Rn] 6d 7s2 |
| Electrons per shell | 2, 8, 18, 32, 18, 9, 2 |
| Electronegativity (Pauling) | 1.1 |
| Atomic radius | 195.0 pm |
| Density | 10.0 g/cm³ |
| First ionisation energy | 5.3802 eV |
| Melting point | 1323.15 K (1050.00 °C) |
| Boiling point | 3473.15 K (3200.00 °C) |
| Common oxidation states | +3 |
Uses
Neutron sources, cancer-therapy research
Discovery
1899, André Debierne