These ideas are covered in the following programmed learning text. Oxidation is most often defined in simple terms as the addition of oxygen or the removal of hydrogen. The following equation shows the oxidation of magnesium to magnesium oxide. The following equation shows the reduction of copper oxide to copper. This illustrates a general principle which is that oxidation and reduction reactions always occur simultaneously.
Respiration involves a series of redox reactions.
The equation for the oxidation of calcium by oxygen is shown below. In terms of the atoms and their constituent electrons, it may be represented as in the diagram. Notice that a redistribution of electrons occurs. A more convenient way of emphasising the redistribution of electrons in this reaction involves considering only the changes in charge that occur. The loss of electrons is associated with oxidation.