Multiple Choice
Which of the following statements correctly describes the Lewis dot structure of the ammonium ion (NH_4^+)?
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11. Bonding & Molecular Structure
Lewis Dot Structures: Ions
Multiple Choice
Which of the following best describes the correct Lewis dot structure for the nitrate ion, NO_3^-?
A
The central nitrogen atom is bonded to two oxygen atoms with double bonds and one oxygen with a single bond, and the single-bonded oxygen carries a positive formal charge.
B
The central nitrogen atom is bonded to three oxygen atoms with three single bonds, and the nitrogen atom carries a negative formal charge.
C
The central nitrogen atom is bonded to three oxygen atoms with one double bond and two single bonds, and each single-bonded oxygen carries a negative formal charge. The structure exhibits resonance among the three oxygen atoms.
D
The central nitrogen atom is bonded to three oxygen atoms with three double bonds, and the structure does not exhibit resonance.
Verified step by step guidance1
Step 1: Determine the total number of valence electrons available for the nitrate ion (NO_3^-). Nitrogen has 5 valence electrons, each oxygen has 6, and the extra negative charge adds 1 more electron. So, total electrons = 5 + (3 × 6) + 1.
Step 2: Draw a skeletal structure with nitrogen as the central atom bonded to three oxygen atoms. Connect each oxygen to nitrogen with a single bond initially.
Step 3: Distribute the remaining valence electrons to satisfy the octet rule for the oxygen atoms first, then place any leftover electrons on the nitrogen atom if needed.
Step 4: To minimize formal charges, convert one of the nitrogen-oxygen single bonds into a double bond. Calculate formal charges for each atom using the formula: \(\text{Formal charge} = \text{Valence electrons} - \text{Nonbonding electrons} - \frac{1}{2} \times \text{Bonding electrons}\).
Step 5: Recognize that the double bond can be placed with any of the three oxygen atoms, creating resonance structures. The correct Lewis structure is a resonance hybrid with one N=O double bond and two N–O single bonds, where the single-bonded oxygens carry negative formal charges.
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