How many peroxide groups are present in $CrO_5$?

What is the correct order of the oxidation state of sulfur in the anions $SO_3^{2-}$,${S_2}O_4^{2-}$,and ${S_2}O_6^{2-}$?

Carbon is in the lowest oxidation state in

What is the oxidation state of oxygen in $OF_2$ and in $KO_2$ respectively?

Calculate the oxidation number of sulfur,chromium,and nitrogen in $H_2SO_5$,$Cr_2O_7^{2-}$,and $NO_3^-$. Suggest the structures of these compounds and explain the fallacy in the direct calculation of the oxidation number for $H_2SO_5$.

What is the oxidation number of sulfur in $Na_2S_4O_6$?