What is the reduction half-reaction for 2Mg + O2 --> 2MgO?

Answer:
Here every atom of oxygen takes in 2 electrons, which means that a molecule of oxygen will take in 4 electrons. On the other hand, the oxidation state of magnesium is going from 0 on the reactants' side to +2 on the products' side, which means that magnesium is being oxidize