Question

What is oxidation number of carbon in $C{N}^{-}$?

(Give the absolute value)

Answer 1

Let $x$ be the oxidation number of $C$ in $C{N}^{-}$ ion. The oxidation number of N is $-3$.
The sum of the oxidation numbers is equal to the charge on the ion.
Hence, $x+(-3)=-1$
or, $x=+2$.
Thus, the oxidation number of $C$ in cyanide ion is $+2$.