What is the average bond order for the N–O bond in the nitrite ion, NO_2^-?

• A. 2.0
• B. 1.5
• C. 1.0
• D. 2.5

Answer: (B)

Verified step by step guidance

1. Identify the Lewis structure of the nitrite ion (NO_2^-). Nitrite has one nitrogen atom bonded to two oxygen atoms and carries an overall negative charge.
2. Determine the total number of valence electrons: Nitrogen has 5, each oxygen has 6, and there is 1 extra electron due to the negative charge. So, total valence electrons = 5 + 2×6 + 1 = 18 electrons.
3. Draw resonance structures for NO_2^-. There are two major resonance forms where one N–O bond is a double bond and the other is a single bond, and these two forms are equivalent and contribute equally.
4. Calculate the bond order for the N–O bonds by averaging the bond orders from the resonance structures. Since one bond is a double bond (bond order 2) and the other is a single bond (bond order 1), the average bond order is given by the formula: \(\text{Bond order} = \frac{2 + 1}{2}\).
5. Simplify the expression to find the average bond order, which represents the effective bond strength and length for the N–O bonds in the nitrite ion.