Figure 85 is a diagram based on a rectangle divided into 3 sections with its longest side running horizontally. The middle section, labelled 'electrolyte (positive and negative ions)', is about 4 times wider than each of the two end sections. The end sections represent the two electrodes in an electrochemical cell. In the left hand electrode there are two black dots labelled 'atoms'. A horizontal curved arrow extends from each dot in the left hand electrode into the centre section. This area of the centre section is labelled 'positive ions'. In the right hand electrode there are also two black dots labelled 'atoms'. A horizontal curved arrow extends from the centre section 'positive ions' to each dot in the right electrode. Above the left hand electrode there is a vertical arrow pointing up to the word 'electrons'. From this word there is a long horizontal arrow going across the top of the rectangle and pointing to another word 'electrons' located directly above the right hand section of the rectangle. From this word, a vertical arrow points down to the right hand electrode. Overall the diagram indicates that atoms can be transferred from the left-hand electrode to the one on the right by first losing electrons. The electrons move to the other electrode by way of an external circuit, whilst the atoms do so as ions in solution that drift through the electrolyte to the other electrode before recombining with the electrons to become neutral atoms once more.

 5.4 Batteries, chemistry and corrosion