The oxidation states of $S$ in $H_2S_2O_7$ are:

The oxidation state of iodine in $I_3^{-}$ is:

Assign the oxidation number to the underlined element in each of the following species:
$1$. $K_2\underline{Mn}O_4$
$2$. $Ca\underline{O}_2$
$3$. $Na\underline{B}H_4$
$4$. $KAl(\underline{S}O_4)_2 \cdot 12H_2O$

The oxidation number of carbon in $CH_2O$ is

Fill in the blanks:
$(1)$ During the reaction $CN^{-} \to CNO^{-}$,......... is added.
$(2)$ The maximum positive oxidation number for any chalcogen compound may be ......... .

Oxidation number of $Mn$ in $K_2MnO_4$ and in $KMnO_4$ are respectively