1. oxygen transfer
   1. oxidation
      1. gain of oxygen
   2. oxidising agent
      1. give oxygen to another substance
   3. reduction
      1. loss of oxygen
   4. reduction agent
      1. takes oxygen from another substance
2. hydrogen
   1. not used much now
   2. oxidation
      1. gain of hydrogen
   3. oxidizing agent
      1. give oxygen to another substance or remove hydrogen from it.
   4. reduction
      1. loss of hydrogen
   5. reduction agent
      1. remove oxygen from another substance or give hydrogen to it.
3. Electron Transfer
   1. OIL RIG
      1. oxidation is loss
      2. reduction is gain
   2. the magnesium is reducing the copper(II) ions by giving them electrons to neutralise the charge. Magnesium is a reducing agent.
   3. the copper(II) ions are removing electrons from the magnesium to create the magnesium ions. The copper(II) ions are acting as an oxidising agent.