Representation of reactions at electrodes as half equations (HT only)

During electrolysis, at the cathode (negative electrode), positively charged ions gain electrons and so the reactions are reductions.

At the anode (positive electrode), negatively charged ions lose electrons and so the reactions are oxidations.

Reactions at electrodes can be represented by half equations, for example:

$$2\mathrm{H^+}+2\mathrm{e^-}\rightarrow\mathrm{H_2}$$