| Molecule | Molecular weight | Kinetic diameter (pm) | Kinetic diameter (Å) | |
| Name | Formula | |||
| Hydrogen | H2 | 2 | 289 | 2.89 |
| Helium | He | 4 | 260 | 2.6 |
| Methane | CH4 | 16 | 380 | 3.8 |
| Water | H2O | 18 | 265 | 2.65 |
| Nitrogen | N2 | 28 | 364 | 3.64 |
| Carbon monoxide | CO | 28 | 376 | 3.76 |
| Nitric oxide | NO | 30 | 317 | 3.17 |
| Oxygen | O2 | 32 | 346 | 3.46 |
| Hydrogen sulfide | H2S | 34 | 360 | 3.6 |
| Hydrogen chloride | HCl | 36 | 320 | 3.2 |
| Carbon dioxide | CO2 | 44 | 330 | 3.3 |
| Nitrous oxide | N2O | 44 | 330 | 3.3 |
| Sulfur dioxide | SO2 | 64 | 360 | 3.6 |
| Chlorine | Cl2 | 70 | 320 | 3.2 |