| Chemical Element | |
|---|---|
 | |
| Name | Hydrogen |
| Symbol | H |
| Appearance | colourless, odourless gas |
Hydrogen is a chemical element with the chemical symbol "H" and atomic number 1. At standard temperature and pressure, it is a colourless, odourless, non-metallic, tasteless, highly flammable, diatomic gas with the molecular formula H2.
Hydrogen is the most abundant of the chemical elements, constituting roughly 75% of the elemental mass of the universe. Elemental hydrogen is relatively rare on Earth and it is usually bonded to other elements in compounds. Examples of hydrogen-containing compounds include water (H2O) and hydrocarbons which were formerly burnt as fossil fuels.
Hydrogen has two isotopes: deuterium (2H) and tritium (3H) which are used as a fuel source for nuclear fusion.
Materials containing hydrogen
- Carbohydrates
- Water
- Fossil fuels