What is the formal charge on the oxygen atom in the Lewis structure of the nitrate ion (NO_3^-), where one oxygen is double-bonded to nitrogen and the other two are single-bonded with each carrying one lone pair?

• A. -2
• B. 0
• C. +1
• D. -1

Answer: (D)

Verified step by step guidance

1. Identify the number of valence electrons for oxygen. Oxygen has 6 valence electrons because it is in group 16 of the periodic table.
2. Determine the number of lone pair electrons on the oxygen atom in question. According to the problem, the oxygen atoms that are single-bonded each have one lone pair, which means 2 electrons are in lone pairs.
3. Count the number of bonding electrons shared with nitrogen. For the single-bonded oxygen, it shares one single bond with nitrogen, which corresponds to 2 bonding electrons. Since formal charge counts half of the bonding electrons, this oxygen atom has 1 electron from bonding.
4. Use the formal charge formula: \(\text{Formal Charge} = \text{Valence Electrons} - \text{Nonbonding Electrons} - \frac{1}{2} \times \text{Bonding Electrons}\) Substitute the values for the single-bonded oxygen: valence electrons = 6, nonbonding electrons = 2 (one lone pair), bonding electrons = 2 (one single bond).
5. Calculate the formal charge by plugging in the numbers: \(\text{Formal Charge} = 6 - 2 - \frac{1}{2} \times 2\) Simplify the expression to find the formal charge on the oxygen atom.