Metal Oxides

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

  • In an oxidation reaction, an element or compound loses electrons, which often results in the addition of oxygen.
  • In a reduction reaction, an element or compound gains electrons, which can lead to the removal of oxygen.

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

Magnesium + Oxygen  Magnesium oxide

2Mg + O2 2MgO

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

On the other hand, metal oxides can lose oxygen, releasing it into the air. For example:

Magnesium oxide Magnesium + Oxygen

2MgO 2Mg + O2

In this reaction, oxygen from the magnesium oxide is released into the air, so the oxygen undergoes reduction. We can also say that the oxygen in magnesium oxide has been reduced.

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