Hydrogen vs Helium
| Property | H Hydrogen | He Helium |
|---|---|---|
| Atomic number | 1 | 2 |
| Symbol | H | He |
| Name | Hydrogen | Helium |
| Category | nonmetal | noble-gas |
| Standard Atomic Weight | 1.007975 u | 4.002602 u |
| Period | 1 | 1 |
| Group | 1 | 18 |
| Block | s | s |
| Phase at STP | gas | gas |
| Electron configuration | 1s1 | 1s2 |
| Oxidation states | [-1, 1] | [0] |
| Electronegativity (Pauling) | 2.2 | N/A |
| Electron affinity | 0.75419 eV | -0.5 eV |
| Density | 0.08988 kg/m³ | 0.1785 kg/m³ |
| Melting point | -259.34 °C | -272.2 °C |
| Boiling point | -252.87 °C | -268.93 °C |
| Discovery year | 1766 | 1868 |