Helium vs Astatine
| Property | He Helium | At Astatine |
|---|---|---|
| Atomic number | 2 | 85 |
| Symbol | He | At |
| Name | Helium | Astatine |
| Category | noble-gas | halogen |
| Standard Atomic Weight | 4.002602 u | 210 u |
| Period | 1 | 6 |
| Group | 18 | 17 |
| Block | s | p |
| Phase at STP | gas | solid |
| Electron configuration | 1s2 | [Xe]6s24f145d106p5 |
| Oxidation states | [0] | [-1, 1, 3, 5, 7] |
| Electronegativity (Pauling) | N/A | 2.2 |
| Electron affinity | -0.5 eV | 2.391 eV |
| Density | 0.1785 kg/m³ | 7000 kg/m³ |
| Melting point | -272.2 °C | 301.85 °C |
| Boiling point | -268.93 °C | -273.15 °C |
| Discovery year | 1868 | 1940 |