Helium vs Francium
| Property | He Helium | Fr Francium |
|---|---|---|
| Atomic number | 2 | 87 |
| Symbol | He | Fr |
| Name | Helium | Francium |
| Category | noble-gas | alkali-metal |
| Standard Atomic Weight | 4.002602 u | 223 u |
| Period | 1 | 7 |
| Group | 18 | 1 |
| Block | s | s |
| Phase at STP | gas | solid |
| Electron configuration | 1s2 | [Rn]7s1 |
| Oxidation states | [0] | [1] |
| Electronegativity (Pauling) | N/A | 0.7 |
| Electron affinity | -0.5 eV | 0.491 eV |
| Density | 0.1785 kg/m³ | 1870 kg/m³ |
| Melting point | -272.2 °C | 26.85 °C |
| Boiling point | -268.93 °C | -273.15 °C |
| Discovery year | 1868 | 1939 |