Promethium vs Actinium
| Property | Pm Promethium | Ac Actinium |
|---|---|---|
| Atomic number | 61 | 89 |
| Symbol | Pm | Ac |
| Name | Promethium | Actinium |
| Category | lanthanide | actinide |
| Standard Atomic Weight | 145 u | 227 u |
| Period | 6 | 7 |
| Group | N/A | N/A |
| Block | s | s |
| Phase at STP | solid | solid |
| Electron configuration | [Xe]6s24f5 | [Rn]7s26d1 |
| Oxidation states | [2, 3] | [3] |
| Electronegativity (Pauling) | N/A | 1.1 |
| Electron affinity | 0.129 eV | 0.35 eV |
| Density | 7260 kg/m³ | 1.007000e+4 kg/m³ |
| Melting point | 1041.85 °C | 1050.85 °C |
| Boiling point | 2999.85 °C | 3197.85 °C |
| Discovery year | 1902 | 1899 |