Key learning for this topic

This is a great topic and it links to so many parts of chemistry but it is especially important that you fully grasp it before moving onto Electrochemistry, Transition metals and Aqueous Ions in year 13. Here, you need to start with identifying the oxidation state (charge) of atoms or ions in compounds, elements or even complexes (more about complexes next year. By working out the charges of know elements, you can workout the unknow oxidation state of another. You are usually looking for those with a varying oxidation state such as transition metals and the non-metals when attached to oxygen. When looking at things like Nitrogen containing ions, Nitrogen only has 5 electrons in its outer shell so the highest state it can reach it +5. Chlorine has 7 in its outer shell so can go as high as +7.

The next stage is a simple GCSE operation. Creating half equations to show a change in oxidation state. Ensure that you can identify oxidation and reduction too. Here are two very simple ones.

REDOX changes that involve ions containing oxygen are balanced in acidic conditions and it is essential that you follow the steps below and always check at the end that the charges balance.

In a REDOX reaction, one species gives electrons to another which receives them. When we combine these half equations, it is critical that we ignore the stoichiometry of the reaction and simply ensure that number of electrons given is equal to the number of electrons received so that they can be cancelled out.

This page was updated on: 4th November 2023