Promethium vs Polonium
| Property | Pm Promethium | Po Polonium |
|---|---|---|
| Atomic number | 61 | 84 |
| Symbol | Pm | Po |
| Name | Promethium | Polonium |
| Category | lanthanide | metalloid |
| Standard Atomic Weight | 145 u | 209 u |
| Period | 6 | 6 |
| Group | N/A | 16 |
| Block | s | p |
| Phase at STP | solid | solid |
| Electron configuration | [Xe]6s24f5 | [Xe]6s24f145d106p4 |
| Oxidation states | [2, 3] | [-2, 2, 4, 5, 6] |
| Electronegativity (Pauling) | N/A | 2 |
| Electron affinity | 0.129 eV | 1.9 eV |
| Density | 7260 kg/m³ | 9320 kg/m³ |
| Melting point | 1041.85 °C | 253.85 °C |
| Boiling point | 2999.85 °C | 961.85 °C |
| Discovery year | 1902 | 1898 |