Question

What is the oxidation number of underlined element?

${\underset{–}{S}}_2{O}_8^{2-}$

Answer 1

$\begin{array}{c}\text{Let oxidation state of Sulphor be '}x\text{'}\\ \text{By oxidation number rule}\\ 2x+6(-2)+2(-1)=-2\Rightarrow x=+6\\ \therefore \text{Oxidation number of Sulphur is}+6\end{array}$