P₄ + 3O₂ - > 2P₂O₃.
This is an oxidation reaction or an addition reaction or a redox reaction.
Step-by-step explanation:
Red Phosphorous reacts with limited oxygen in low temperature to form phosphorous trioxide which readily dimerises to form tetraphosphorous hexaoxide. This molecule is actually an anhydride of phosphorous acid, but it's not obtained from the acid itself by dehydration.
This is a type of oxidation reaction, as well as a redox reaction where oxygen is reduced and phosphorous is oxidized. It's also an addition reaction where two reactants produce a single product.
Its balanced by adding 3 before oxygen and 2 before phosphorous trioxide.