Rubidium vs Promethium
| Property | Rb Rubidium | Pm Promethium |
|---|---|---|
| Atomic number | 37 | 61 |
| Symbol | Rb | Pm |
| Name | Rubidium | Promethium |
| Category | alkali-metal | lanthanide |
| Standard Atomic Weight | 85.4678 u | 145 u |
| Period | 5 | 6 |
| Group | 1 | N/A |
| Block | s | s |
| Phase at STP | solid | solid |
| Electron configuration | [Kr]5s1 | [Xe]6s24f5 |
| Oxidation states | [-1, 1] | [2, 3] |
| Electronegativity (Pauling) | 0.82 | N/A |
| Electron affinity | 0.4859 eV | 0.129 eV |
| Density | 1530 kg/m³ | 7260 kg/m³ |
| Melting point | 39.31 °C | 1041.85 °C |
| Boiling point | 687.85 °C | 2999.85 °C |
| Discovery year | 1861 | 1902 |