The peroxides contain O₂^2- (isoelectronic to F₂)
(i)    Li₂O₂ is prepared by the reaction of LiOH. H₂O with H₂O₂ and dehydration of the subsequent hyperperoxide by gentle heating under reduced pressure

LiOH.H₂O + H₂O₂  →  LiOOH.H₂O + H₂O
        2LiOOH.H₂O    →   Li₂O₂ + H₂O₂ + H₂O

(ii)    Na₂O₂ is prepared by oxidizing Na to Na₂O in a limited supply of air and then allowing it to react with more O₂ to give a pale-yellow powder of Na₂O₂

                                      1/2O₂
2Na + 1 O₂   →  Na₂O    →     Na₂O₂
        2                                         (pale-yellow)

(iii)    The heavier alkali metal peroxides cannot be prepared by the above method because of their further oxidation to superoxides, MO₂. They are best prepared by the quantitative oxidation of the metals in liquid NH₃.

       e^-_am               e^-_am
O₂     →        O₂^-     →   O₂^2-

Sodium peroxide (NaO₂) finds use in industry as a bleaching agent for fabrics, paper, pulp, wood etc. It is also used as a powerful oxidizing agent. Its reactions with CO and CO₂ give Na₂ CO₃.

  Na₂O₂ + CO   →    Na₂CO₃
Na₂O₂ + CO₂   →    Na₂CO₃ + 1  O₂
                                                  2
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