The Basics[]
Redox is short for Reduction-Oxidation.
No reaction can only involve Reduction or only involve Oxidation.
Anything gaining electrons is reduced but they have to take the electrons from another substance. This substance will be oxidised.
Exam Hint[]
Redox is all about electron-transfer but oxidation numbers are an easier way to spot what is going on.
Know how to work out Oxidation Numbers.
Increasing Oxidation Number is Oxidation.
Reducing Oxidation Number is Reduction.
Don't forget O.I.L.R.I.G. - Oxidation Is Loss (of electrons), Reduction Is Gain (of electrons) - you may be asked to explain Redox in terms of electron transfer.