| Element | Actinium | Symbol | Ac |
| Atomic Number | 89 | Molar Mass | 227.03 g mol-1 |
| Electron Configuration | [Rn]6d17s2 | Normal State | solid metal |
| Density @STP | 10.07 g cm-3 | Melting Point | 1051oC |
| Boiling Point | 3200oC | Stable Isotopes | 169Tm |
| Atomic Radius | 188 pm | Ionic Radius | 118 (4+) pm |
| Electronegativity (Pauling) | 1.1 | Ionization Energy (1st) | 499 kJ mol-1 |
| Ionization Energy (2nd) | 1170 kJ mol-1 | Ionization Energy (3rd) | 1900 kJ mol-1 |
| Molar Heat Capacity | 27.2 J K-1mol-1 | Standard Molar Entropy | 56.5 J K-1mol-1 |
| Enthalpy of Fusion | 14.2 kJ mol-1 | Enthalpy of Vapourization | 418 kJ mol-1 |