Argon vs Promethium
| Property | Ar Argon | Pm Promethium |
|---|---|---|
| Atomic number | 18 | 61 |
| Symbol | Ar | Pm |
| Name | Argon | Promethium |
| Category | noble-gas | lanthanide |
| Standard Atomic Weight | 39.948 u | 145 u |
| Period | 3 | 6 |
| Group | 18 | N/A |
| Block | p | s |
| Phase at STP | gas | solid |
| Electron configuration | [Ne]3s23p6 | [Xe]6s24f5 |
| Oxidation states | [0] | [2, 3] |
| Electronegativity (Pauling) | N/A | N/A |
| Electron affinity | -1 eV | 0.129 eV |
| Density | 1.7837 kg/m³ | 7260 kg/m³ |
| Melting point | -189.35 °C | 1041.85 °C |
| Boiling point | -185.85 °C | 2999.85 °C |
| Discovery year | 1894 | 1902 |