In which of the following pairs of compounds, nitrogen has maximum positive and maximum negative values of oxidation number? 

Solution:

Nitrogen in ${\mathrm{HNO}}_3$ and $\mathrm{HCN}$ has +5 and -5 oxidation number, respectively. These are the maximum positive or negative amongst the oxidation of number of N in other substances.

The oxidation number, sometimes referred to as the oxidation state, is the total number of electrons that an atom gains or loses while uniting with another atom to form a chemical bond.