Arsenic vs Selenium
| Property | As Arsenic | Se Selenium |
|---|---|---|
| Atomic number | 33 | 34 |
| Symbol | As | Se |
| Name | Arsenic | Selenium |
| Category | metalloid | nonmetal |
| Standard Atomic Weight | 74.921595 u | 78.971 u |
| Period | 4 | 4 |
| Group | 15 | 16 |
| Block | p | p |
| Phase at STP | solid | solid |
| Electron configuration | [Ar]4s23d104p3 | [Ar]4s23d104p4 |
| Oxidation states | [-3, -2, -1, 0, 1, 2, 3, 4, 5] | [-2, -1, 0, 1, 2, 3, 4, 5, 6] |
| Electronegativity (Pauling) | 2.18 | 2.55 |
| Electron affinity | 0.81 eV | 2.0206 eV |
| Density | 5776 kg/m³ | 4809 kg/m³ |
| Melting point | 816.85 °C | 220.5 °C |
| Boiling point | 613.85 °C | 684.85 °C |
| Discovery year | 1250 | 1817 |