The superoxides contain the paramagnetic O₂^- ion (refer to M.O. theory, B.SC. Part I  book).
(i)    LiO₂ is prepared by matrix isolation experiments at 15 k.

(ii)    NaO₂ is prepared by reacting Na with O₂ at 4500C and 150 atm. pressure.

(iii)    Heavier alkali metals form KO₂ (orange), RbO₂ (brown) and CsO₂ (orange) as normal products when these elements are burnt in air. The heavier peroxides show the tetragonal CaC₂ structure.

For more help in Superoxides click the button below to submit your homework assignment