Final answer:
In the Lewis structure for the nitrate ion, NO3−, nitrogen forms three covalent bonds, consisting of two single bonds and one double bond in one resonance form. However, due to resonance, the actual bond character is a blend between single and double bonds, leading to equal and shorter bond lengths.
Step-by-step explanation:
The nitrate ion (NO3−) has a Lewis structure that is made up of resonance forms. In a single resonance structure, nitrogen forms two single bonds and one double bond with the three oxygen atoms. However, due to resonance, the actual structure of the nitrate ion is a hybrid of these contributing forms. Each nitrogen-oxygen bond in the nitrate ion is a blend of a single and a double bond, which makes the bond lengths equal and shorter than a typical single bond.
When we count up the valence electrons for the nitrate ion, we have a total of (1*5) from nitrogen, (3*6) from oxygen, plus 1 extra electron because it is an ion, giving us 24 electrons to work with. This leads to a Lewis structure where the nitrogen has one lone pair of electrons and forms three covalent bonds with the oxygen atoms. It is also important to note that the formal charges are distributed in such a way that the overall charge of the ion is − 1.