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

The difference in the oxidation numbers of the two types of sulphur atoms in $Na_2S_4O_6$ is

What is the oxidation state of carbon in $CaC_2$ and $K_2C_2O_4$ respectively?

Suggest a list of substances where carbon can exhibit oxidation states from $-4$ to $+4$ and nitrogen can exhibit oxidation states from $-3$ to $+5$.

What is the oxidation state of phosphorus in $Ba(H_2PO_2)_2$?

Assertion: The average oxidation number of sulfur in $Na_2S_4O_6$ is $2.5$.
Reason: Two $S$ atoms are not directly bonded to $O$-atoms.