Helium vs Argon
| Property | He Helium | Ar Argon |
|---|---|---|
| Atomic number | 2 | 18 |
| Symbol | He | Ar |
| Name | Helium | Argon |
| Category | noble-gas | noble-gas |
| Standard Atomic Weight | 4.002602 u | 39.948 u |
| Period | 1 | 3 |
| Group | 18 | 18 |
| Block | s | p |
| Phase at STP | gas | gas |
| Electron configuration | 1s2 | [Ne]3s23p6 |
| Oxidation states | [0] | [0] |
| Electronegativity (Pauling) | N/A | N/A |
| Electron affinity | -0.5 eV | -1 eV |
| Density | 0.1785 kg/m³ | 1.7837 kg/m³ |
| Melting point | -272.2 °C | -189.35 °C |
| Boiling point | -268.93 °C | -185.85 °C |
| Discovery year | 1868 | 1894 |