Helium vs Rubidium
| Property | He Helium | Rb Rubidium |
|---|---|---|
| Atomic number | 2 | 37 |
| Symbol | He | Rb |
| Name | Helium | Rubidium |
| Category | noble-gas | alkali-metal |
| Standard Atomic Weight | 4.002602 u | 85.4678 u |
| Period | 1 | 5 |
| Group | 18 | 1 |
| Block | s | s |
| Phase at STP | gas | solid |
| Electron configuration | 1s2 | [Kr]5s1 |
| Oxidation states | [0] | [-1, 1] |
| Electronegativity (Pauling) | N/A | 0.82 |
| Electron affinity | -0.5 eV | 0.4859 eV |
| Density | 0.1785 kg/m³ | 1530 kg/m³ |
| Melting point | -272.2 °C | 39.31 °C |
| Boiling point | -268.93 °C | 687.85 °C |
| Discovery year | 1868 | 1861 |