| name | Actinium |
| latin | Actinium |
| french | Actinium |
| german | Actinium |
| symbol | Ac |
| proton number | 89 |
| atomic weight | 227.0278 |
| Pauling electronegativity | 1.1 |
| electronic configuration | [Rn] 6d17s2 1s22s22p63s23p63d104s24p64d105s25p64f145d106s26p66d17s2 |
| melting point | 1323 K, 1050°C, 1922°F |
| boiling point | 3573 K, 3300°C, 5972°F |
| group | 3 |
| period | 7 |
| state (by 20°C) | solid |
| oxidation states | +3 |
| Year of discovery | Discoverer |
| 1899 | Andre Debierne |