Oxidation number of potassium in $K_2O$,$K_2O_2$ and $KO_2$,respectively,is

The oxidation number of sulphur in $S_8$ molecule is

Oxidation number of $As$ atoms in $H_3AsO_4$ is

Write the oxidation number of oxygen in $KO_{3}$ and $Na_{2}O_{2}$.

The sum of the oxidation numbers of all atoms in the $S_{2}O_{3}^{2-}$ ion is:

Consider the following compounds:
$\underline{K}O_2$,$H_2\underline{O}_2$ and $H_2\underline{S}O_4$.
The oxidation states of the underlined elements in them are,respectively,