Helium vs Thulium
| Property | He Helium | Tm Thulium |
|---|---|---|
| Atomic number | 2 | 69 |
| Symbol | He | Tm |
| Name | Helium | Thulium |
| Category | noble-gas | lanthanide |
| Standard Atomic Weight | 4.002602 u | 168.93422 u |
| Period | 1 | 6 |
| Group | 18 | N/A |
| Block | s | s |
| Phase at STP | gas | solid |
| Electron configuration | 1s2 | [Xe]6s24f13 |
| Oxidation states | [0] | [0, 1, 2, 3] |
| Electronegativity (Pauling) | N/A | 1.25 |
| Electron affinity | -0.5 eV | 1.029 eV |
| Density | 0.1785 kg/m³ | 9320 kg/m³ |
| Melting point | -272.2 °C | 1544.85 °C |
| Boiling point | -268.93 °C | 1949.85 °C |
| Discovery year | 1868 | 1879 |