Cesium vs Promethium
| Property | Cs Cesium | Pm Promethium |
|---|---|---|
| Atomic number | 55 | 61 |
| Symbol | Cs | Pm |
| Name | Cesium | Promethium |
| Category | alkali-metal | lanthanide |
| Standard Atomic Weight | 132.905452 u | 145 u |
| Period | 6 | 6 |
| Group | 1 | N/A |
| Block | s | s |
| Phase at STP | solid | solid |
| Electron configuration | [Xe]6s1 | [Xe]6s24f5 |
| Oxidation states | [-1, 1] | [2, 3] |
| Electronegativity (Pauling) | 0.79 | N/A |
| Electron affinity | 0.4716 eV | 0.129 eV |
| Density | 1930 kg/m³ | 7260 kg/m³ |
| Melting point | 28.44 °C | 1041.85 °C |
| Boiling point | 670.85 °C | 2999.85 °C |
| Discovery year | 1860 | 1902 |