How do you determine the oxidation state of an element in a compound?

The oxidation state of an element in a compound can be determined by assigning oxidation numbers to each element in the compound. The oxidation number is a measure of the number of electrons an atom in a compound has gained or lost relative to its pure element state.

There are several rules to assign oxidation numbers:

• The oxidation number of a pure element is zero.
• The oxidation number of an ion is equal to its charge.
• The sum of oxidation numbers of all atoms in a neutral compound is zero.
• In a polyatomic ion, the sum of oxidation numbers of all atoms is equal to the charge of the ion.
• Oxygen has an oxidation number of -2 in most compounds, except for peroxides where it has an oxidation number of -1.
• Hydrogen has an oxidation number of +1 when bonded to a non-metal and -1 when bonded to a metal.

By applying these rules, the oxidation state of each element in a compound can be determined.