Selected atom
| Atom | none |
| Element | — |
| Atomic number | — |
| Atomic weight | — |
| Electronegativity (Pauling) | — |
| Valence (common) | — |
| Notes | — |
“Specific gravity” context
| H₂ relative density (air=1) | ~0.07 |
| O₂ relative density (air=1) | ~1.10 |
| H₂ density (STP) | ~0.090 g/L |
| O₂ density (STP) | ~1.429 g/L |