Selenium vs Actinium
| Property | Se Selenium | Ac Actinium |
|---|---|---|
| Atomic number | 34 | 89 |
| Symbol | Se | Ac |
| Name | Selenium | Actinium |
| Category | nonmetal | actinide |
| Standard Atomic Weight | 78.971 u | 227 u |
| Period | 4 | 7 |
| Group | 16 | N/A |
| Block | p | s |
| Phase at STP | solid | solid |
| Electron configuration | [Ar]4s23d104p4 | [Rn]7s26d1 |
| Oxidation states | [-2, -1, 0, 1, 2, 3, 4, 5, 6] | [3] |
| Electronegativity (Pauling) | 2.55 | 1.1 |
| Electron affinity | 2.0206 eV | 0.35 eV |
| Density | 4809 kg/m³ | 1.007000e+4 kg/m³ |
| Melting point | 220.5 °C | 1050.85 °C |
| Boiling point | 684.85 °C | 3197.85 °C |
| Discovery year | 1817 | 1899 |