Oxygen vs Selenium
| Property | O Oxygen | Se Selenium |
|---|---|---|
| Atomic number | 8 | 34 |
| Symbol | O | Se |
| Name | Oxygen | Selenium |
| Category | nonmetal | nonmetal |
| Standard Atomic Weight | 15.9994 u | 78.971 u |
| Period | 2 | 4 |
| Group | 16 | 16 |
| Block | p | p |
| Phase at STP | gas | solid |
| Electron configuration | [He]2s22p4 | [Ar]4s23d104p4 |
| Oxidation states | [-2, -1, 0, 1, 2] | [-2, -1, 0, 1, 2, 3, 4, 5, 6] |
| Electronegativity (Pauling) | 3.44 | 2.55 |
| Electron affinity | 1.4611 eV | 2.0206 eV |
| Density | 1.429 kg/m³ | 4809 kg/m³ |
| Melting point | -218.79 °C | 220.5 °C |
| Boiling point | -182.95 °C | 684.85 °C |
| Discovery year | 1771 | 1817 |