Which of the following is the correct Lewis dot structure for the azide ion (N₃⁻)?

• A. N-N≡N with a lone pair on the central nitrogen
• B. N=N=N with no lone pairs
• C. N⁻-N=N⁺ with a lone pair on the central nitrogen
• D. N≡N⁺-N⁻ with a lone pair on the terminal nitrogen

Answer: (D)

Verified step by step guidance

1. Understand that the azide ion (N₃⁻) consists of three nitrogen atoms and carries a negative charge. The goal is to distribute electrons to satisfy the octet rule for each nitrogen atom while accounting for the overall charge.
2. Calculate the total number of valence electrons available. Each nitrogen atom has 5 valence electrons, and the ion has an additional electron due to the negative charge, giving a total of 16 valence electrons.
3. Arrange the nitrogen atoms linearly and begin by placing a single bond between each pair of nitrogen atoms. This initial setup uses 4 electrons, leaving 12 electrons to distribute.
4. Distribute the remaining electrons to satisfy the octet rule for each nitrogen atom. Consider placing triple bonds and lone pairs where necessary. The structure N≡N⁺-N⁻ with a lone pair on the terminal nitrogen satisfies the octet rule and accounts for the charge distribution.
5. Verify the formal charges for each nitrogen atom in the structure. The terminal nitrogen with a lone pair should have a formal charge of -1, the central nitrogen should have a formal charge of +1, and the other terminal nitrogen should have a formal charge of 0, ensuring the overall charge of the ion is -1.