Oxidation state of oxygen in $F_2O$ is

What is the oxidation state of $S$ in $SO_4^{2-}$?

The oxidation number of $S$ in $H_2S_2O_8$ is

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 $H_2SO_5$.

In which of the following compounds is the oxidation number of iodine fractional?

Calculate the oxidation number of sulphur,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 calculated oxidation number for $H_2SO_5$.