Selenium vs Astatine
| Property | Se Selenium | At Astatine |
|---|---|---|
| Atomic number | 34 | 85 |
| Symbol | Se | At |
| Name | Selenium | Astatine |
| Category | nonmetal | halogen |
| Standard Atomic Weight | 78.971 u | 210 u |
| Period | 4 | 6 |
| Group | 16 | 17 |
| Block | p | p |
| Phase at STP | solid | solid |
| Electron configuration | [Ar]4s23d104p4 | [Xe]6s24f145d106p5 |
| Oxidation states | [-2, -1, 0, 1, 2, 3, 4, 5, 6] | [-1, 1, 3, 5, 7] |
| Electronegativity (Pauling) | 2.55 | 2.2 |
| Electron affinity | 2.0206 eV | 2.391 eV |
| Density | 4809 kg/m³ | 7000 kg/m³ |
| Melting point | 220.5 °C | 301.85 °C |
| Boiling point | 684.85 °C | -273.15 °C |
| Discovery year | 1817 | 1940 |