Helium vs Oxygen
| Property | He Helium | O Oxygen |
|---|---|---|
| Atomic number | 2 | 8 |
| Symbol | He | O |
| Name | Helium | Oxygen |
| Category | noble-gas | nonmetal |
| Standard Atomic Weight | 4.002602 u | 15.9994 u |
| Period | 1 | 2 |
| Group | 18 | 16 |
| Block | s | p |
| Phase at STP | gas | gas |
| Electron configuration | 1s2 | [He]2s22p4 |
| Oxidation states | [0] | [-2, -1, 0, 1, 2] |
| Electronegativity (Pauling) | N/A | 3.44 |
| Electron affinity | -0.5 eV | 1.4611 eV |
| Density | 0.1785 kg/m³ | 1.429 kg/m³ |
| Melting point | -272.2 °C | -218.79 °C |
| Boiling point | -268.93 °C | -182.95 °C |
| Discovery year | 1868 | 1771 |