Transfer of electrons occurs in displacement reactions of metals. An example of a displacement reaction of metals is given by the chemical equation
 K_{2} CO_{3} (aq) + Ca(NO _{3} )_{2}(aq)CaCO_{3}(s)+2KNO_{3}(aq).
From the chemical equation, an ionic equation can be formed,
From the ionic equation, it can be seen that calcium ions have gained electrons whereas carbonate ions have donated electrons, resulting an ionic bond. In this reaction, energy is lost in the form of heat to produce an ionic bond.