Metal Oxides

Metals react with oxygen in the air to form metal oxides. These are redox reactions.

  • In an oxidation reaction, oxygen is added to the element or compound
  • In a reduction reaction, oxygen is removed from the element or compound

For example, let’s look at the reaction between magnesium and oxygen, which forms magnesium oxide:

Magnesium + Oxygen  Magnesium oxide

Mg + O MgO

In this reaction, magnesium gains oxygen, so it is an oxidation reaction. We can also say that the magnesium has been oxidised.

On the other hand, metal oxides can lose oxygen. For example:

Magnesium oxide Magnesium + Oxygen

MgO Mg + O

In this reaction, magnesium oxide loses oxygen, so it is a reduction reaction. We can also say that magnesium oxide has been reduced.