Because of their strong tendency to become ions, the alkali metals are extremely strong reducing agents. For example,

The metals cannot be obtained from their salts by purely chemical means, and the only practical method is the electrolysis process introduced in Chapter 5, in which an electric current is passed through the appropriate molten salt (see right). Electrons from the outside circuit combine with the cations at the cathode and reduce them to pure metal. At the anode, electrons are donated by the anions and flow out to the external circuit again. For potassium chloride the reactions are

Cathode:
Anode:

Positive and negative ions migrate between the electrodes within the molten salt. The energy needed to reduce the potassium ions and oxidize the chloride ions is supplied by outside electrical energy.