This is copied from an old answer, and attempts to explain the difference between #"oxides"#, #"peroxides"#, and #"superoxides"#....
Most oxygen containing compounds are OXIDES....i.e. they feature oxygen in its stable #stackrel(-II)O# oxidation state. Water, certainly features oxygen with this designation....
Now hydrogen peroxide is #HO-OH#, and it clearly contains an #O-O# bond. Because our definition of oxidation number is #"the charge left on the central atom when all the bonding pairs"# #"of electrons are BROKEN, with the charge assigned"# #"to the most electronegative atom,"# this exercise results in the sharing of the electrons (because the oxygen atoms have equal electronegativity):
i.e. #HO-OHrarr2xxdotOH#
(#dotOH# is the so-called hydroperoxyl radical). The oxygen in hydrogen peroxide has a formal oxidation of #-I#.
And when we write peroxide salts, i.e. sodium peroxide, we use a formula of #Na_2O_2#; i.e. a salt of #""^(-)O-O^-#.
And for #"superoxides"#, to continue the formalism, we write #O_2^-#, that is a mixed oxidation state dioxide of #O^(0)# and #O^(-)#, to give an average oxidation number of #O^(-1/2)#. In very old literature, this goes by the label #"hyperoxide"#.
