The nitrate ion, NO₃⁻, exhibits three equivalent N–O bond lengths even though simple Lewis structures suggest one nitrogen–oxygen double bond and two single bonds.
Answer the following questions about the bonding in NO₃⁻.
(a) Draw all valid resonance structures for the nitrate ion, including formal charges.
(b) Based on the resonance structures, calculate the average (fractional) bond order for an N–O bond in NO₃⁻.
(c) Determine the hybridization state of the nitrogen atom in NO₃⁻.
(d) Using your answers to parts (b) and (c), explain why all three N–O bonds in nitrate are experimentally found to be the same length.