Helium vs Chlorine
| Property | He Helium | Cl Chlorine |
|---|---|---|
| Atomic number | 2 | 17 |
| Symbol | He | Cl |
| Name | Helium | Chlorine |
| Category | noble-gas | halogen |
| Standard Atomic Weight | 4.002602 u | 35.4515 u |
| Period | 1 | 3 |
| Group | 18 | 17 |
| Block | s | p |
| Phase at STP | gas | gas |
| Electron configuration | 1s2 | [Ne]3s23p5 |
| Oxidation states | [0] | [-1, 1, 2, 3, 4, 5, 6, 7] |
| Electronegativity (Pauling) | N/A | 3.16 |
| Electron affinity | -0.5 eV | 3.6127 eV |
| Density | 0.1785 kg/m³ | 3.214 kg/m³ |
| Melting point | -272.2 °C | -101.5 °C |
| Boiling point | -268.93 °C | -34.04 °C |
| Discovery year | 1868 | 1774 |