What are the ionic half-equations for the reactions occurring at the electrodes during aluminium extraction?

In the process of aluminium extraction through electrolysis, the reactions taking place at the electrodes can be expressed as half-equations that clarify the transfer of electrons.

The correct half-equations depict the reduction and oxidation processes happening at the cathode and anode, respectively. At the cathode, aluminium ions (Al³⁺) gain three electrons (3e⁻) to form molten aluminium metal (Al). This describes a reduction reaction as the aluminium ions are being reduced by accepting electrons.

At the anode, oxide ions (O²⁻) are oxidized to form oxygen gas (O₂). The balanced part of this half-reaction shows that for every two oxide ions, a molecule of oxygen gas is produced along with the release of four electrons (4e⁻). This reaction indicates oxidation, where the negatively charged oxide ions lose electrons.

The choice accurately illustrates these two processes in a cohesive manner: aluminium being reduced at the cathode and oxide ions being oxidized at the anode. Therefore, option B effectively captures the correct ionic half-equations for aluminium extraction by identifying the reactions occurring at both electrodes with the correct stoichiometry.