CHEMISTRY · Multi-part · AP · Chemistry · Compound Structure and Properties · Compound Structure and Properties
Problem
Nitrate ion, NO3−, is used extensively as a water–soluble plant nutrient. Although the ion is often represented with one double bond and two single bonds, experimental measurements show that all three N–O bond lengths are identical.
Answer the following questions about the bonding in nitrate.
(a) Draw all valid Lewis resonance structures of the nitrate ion using curved-arrow notation to indicate the movement of electrons between any two adjacent resonance contributors.
(b) For each resonance structure, assign formal charges to every atom. Then describe how the formal charges are distributed among the three oxygen atoms across the full set of resonance contributors.
(c) Explain why the experimentally determined N–O bond lengths are identical, even though individual resonance structures contain both N=O and N–O bonds.
(d) Based on the formal-charge analysis, predict the partial (average) charge on each oxygen atom in the resonance hybrid. Justify your answer quantitatively using the formal-charge data from part (b).