In $Na_2S_4O_6$,the oxidation number of $S$ is

What is the oxidation number of chlorine in $ClO_3^-$?

Oxidation numbers of $P$ in $PO_4^{3-}$,$S$ in $SO_4^{2-}$ and that of $Cr$ in $Cr_2O_7^{2-}$ are respectively

Calculate the oxidation number of oxygen in potassium ozonide $(KO_3)$.

From the given list,the number of compounds with $+4$ oxidation state of Sulphur is $ . . . . . . $.
$SO_3, H_2SO_3, SOCl_2, SF_4, BaSO_4, H_2S_2O_7$

Assertion: In some cases,oxygen exhibits a positive oxidation state. Consequently,it is an electronegative element.
Reason: Fluorine is more electronegative than oxygen.