1. Depending on the ease with the metals lose their electrons and form ions – they are arranged in a series known as – metal activity series or electro chemical series. The arrangement is so done that the elements that – ionize most readily [discharged with great difficulty]- are placed at the top of the series and other elements in the descending order.
2. Selective discharge of ions: The preferential discharge of ions present in an electrolyte at the respective electrodes is known as selective discharge of ions.
It depends upon the following factors:
Relative position of the ion in the electo chemical series: Lower the position of the ion in the series, easier to discharge.
Concentration of the ion: More the concentration of the ion, easier to discharge.
Nature of the electrode: Inert electrodes (graphite, platinum) do not take part in the electrolytic reaction. Active electrodes (Cu electrodes for electrolysis of aq. CuSO4 , Ag electrodes for electrolysis of aq. AgNO3 etc.) take part in electrolytic reactions.
