The reaction of iron with oxygen to form iron oxide is an example of an oxidation–reduction reaction: 4fe + 3o2 → 2fe2o3. in this reaction gains electrons and is .

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Oxygen gains electrons and is reduced.

Explanation:-

For this reaction the balanced chemical equation is

4Fe + 3O2 --> 2Fe2O3

When Oxygen is present as oxygen gas, the oxidation number of O is Zero since it is the only element present in Oxygen gas.

Similarly Iron is present in Fe with oxidation number Zero.

In the case of Fe2O3, Oxygen has the oxidation number -2 while Iron has +3.

So the oxidation number of Oxygen goes from Zero to -2.

Since the oxidation number decreases Oxygen is reduced.

Since reduction involves gain of electrons, Oxygen gains electrons.