Quick trick to memorise the oxidation number of atoms
- The arrow means that an atom 'dominates' over another atom.
- When an atom 'dominates', it means that it will retain its normal oxidation number. For example, as Al dominates over H, Al will retain its +3 number and force H to change from its usual +1 to a -1.
- In exams, do not use the term 'dominate'. It is not an official term and is merely used to explain this memorisation trick.
