Promethium vs Francium
| Property | Pm Promethium | Fr Francium |
|---|---|---|
| Atomic number | 61 | 87 |
| Symbol | Pm | Fr |
| Name | Promethium | Francium |
| Category | lanthanide | alkali-metal |
| Standard Atomic Weight | 145 u | 223 u |
| Period | 6 | 7 |
| Group | N/A | 1 |
| Block | s | s |
| Phase at STP | solid | solid |
| Electron configuration | [Xe]6s24f5 | [Rn]7s1 |
| Oxidation states | [2, 3] | [1] |
| Electronegativity (Pauling) | N/A | 0.7 |
| Electron affinity | 0.129 eV | 0.491 eV |
| Density | 7260 kg/m³ | 1870 kg/m³ |
| Melting point | 1041.85 °C | 26.85 °C |
| Boiling point | 2999.85 °C | -273.15 °C |
| Discovery year | 1902 | 1939 |