In most compounds, the oxidation number of hydrogen is +1.
Key Points:
- Hydrogen usually forms a bond with nonmetals (like oxygen, nitrogen, chlorine). In these cases, hydrogen is less electronegative, so it is assigned +1.
- Example in words: In water, each hydrogen has an oxidation number of +1.
Exceptions:
- When hydrogen is bonded to metals in metal hydrides (like sodium hydride or calcium hydride), it has an oxidation number of –1 because here hydrogen is more electronegative than the metal.
Simple answer: Hydrogen is usually +1 in compounds, except in hydrides where it is –1.