To determine the number of bond pairs and lone pairs on the nitrogen atom in the nitrate ion ($NO_{3}^{-}$), we apply the principles of Lewis structures and covalency. Nitrogen is a second-period element with five valence electrons . In $NO_{3}^{-}$, the total number of valence electrons is 24 (5 from $N$, 18 from three $O$ atoms, and 1 from the negative charge). The nitrogen atom acts as the central atom and forms four bonds—one double bond and two single bonds—to complete the octets of the surrounding oxygen atoms . This results in 4 bond pairs shared by the nitrogen atom. Because the maximum covalency of nitrogen is 4 and it cannot expand its octet due to the absence of d-orbitals, all available bonding capacity is used, leaving 0 lone pairs on the nitrogen atom .