What is the oxidation number of hydrogen in most compounds?

• A. -1
• B. 0
• C. +1
• D. +2

Answer: (C)

In most compounds, hydrogen has a positive oxidation number because it tends to lose its one valence electron when bonded to more electronegative elements. When assigning oxidation numbers, we imagine the bonding electrons going to the more electronegative atom. Since hydrogen is less electronegative than elements like carbon, oxygen, or halogens, it is treated as if it has donated its electron, giving hydrogen an oxidation number of +1.

There are exceptions to remember: in metal hydrides (like NaH) hydrogen can have an oxidation number of -1, and in molecular hydrogen (H2) the oxidation number is 0 because it’s in its elemental form. But in the vast majority of compounds beyond those cases, hydrogen is +1.