Consider the azide ion N3-1. Its general shape is X-X-X. A number of Lewis structures are possible. Do a Lewis calculation and select the correct statement
A. All the possible Lewis structures involve an “sp2” hybridization for the central atom
B. Because the central atom lacks a lone pair in the most favorable Lewis structure, the shape of the molecule is linear
C. There are two Lewis structures with a triple bond that form a resonance pair. They are the best choice for the electronic structure because their formal charges are minimal
D. All of the above statements are true
E. None of the above statements are true
The correct answer and explanation is:
The correct answer is:
B. Because the central atom lacks a lone pair in the most favorable Lewis structure, the shape of the molecule is linear.
Explanation:
The azide ion (N3−N_3^-) consists of three nitrogen atoms in a linear arrangement. To determine the best Lewis structures, we follow these steps:
- Calculate the total valence electrons
- Each nitrogen atom has 5 valence electrons.
- The negative charge (−1-1) adds one extra electron.
- Total electrons: 3×5+1=163 \times 5 + 1 = 16 valence electrons.
- Draw possible structures
Possible Lewis structures include different arrangements of single, double, and triple bonds while maintaining the octet rule. The most favorable resonance structures involve the following:- Structure 1: \ce[N≡N−N]−\ce{[N≡N-N]^-}
- Structure 2: \ce[N=N≡N]−\ce{[N=N≡N]^-}
- Determine formal charges
The best Lewis structures minimize formal charges, calculated as: Formal charge=valence electrons−lone pairs−bonding electrons2\text{Formal charge} = \text{valence electrons} – \text{lone pairs} – \frac{\text{bonding electrons}}{2} The most stable resonance structure has formal charges of 0,+1,−10, +1, -1, rather than extreme charges like −2-2 or +2+2. - Molecular shape and hybridization
- The central nitrogen atom (N) forms two double bonds in resonance and lacks lone pairs.
- Since it is surrounded by two atoms and no lone pairs, it adopts a linear geometry (180° bond angle).
- The central atom is sp-hybridized, not sp², making option A incorrect.
- Why option C is incorrect
- The best resonance forms do not both have a triple bond.
- There is one triple bond in each resonance structure, but not in both simultaneously.
Since only option B is correct, the correct choice is B.
Now, generating the Lewis structure image.
Here is the detailed diagram of the Lewis structure for the azide ion (N3−N_3^-), including resonance structures, lone pairs, formal charges, and bond types. Let me know if you need any modifications or further explanations!
