Determine the shape and bond angle of these oxynitrogen ions. Linear Trigonal planar Tetrahedral Bent Pyramidal 180° 120° 109.5° ~120° ~109° ~109° Answer Bank NO- NO3- NO2- None
The Correct Answer and Explanation is:
To determine the shape and bond angles of the oxynitrogen ions (NO⁻, NO₃⁻, and NO₂⁻), we use Valence Shell Electron Pair Repulsion (VSEPR) theory, which predicts the geometry of a molecule based on the repulsion between electron pairs around a central atom.
1. NO⁻ (Nitrosyl anion)
- Lewis structure: One nitrogen atom is bonded to one oxygen atom with a double bond and has a lone pair on nitrogen.
- Electron domains around N: 2 (1 bonding region, 1 lone pair).
- Electron geometry: Linear.
- Molecular shape: Linear.
- Bond angle: 180°.
2. NO₃⁻ (Nitrate ion)
- Lewis structure: Nitrogen is bonded to three oxygens. It forms one double bond and two single bonds with resonance, making all N–O bonds equivalent.
- Electron domains around N: 3 bonding pairs, no lone pairs.
- Electron geometry: Trigonal planar.
- Molecular shape: Trigonal planar.
- Bond angle: 120°.
3. NO₂⁻ (Nitrite ion)
- Lewis structure: Nitrogen is bonded to two oxygens with one double bond and one single bond (resonance between them). There is also a lone pair on nitrogen.
- Electron domains around N: 3 (2 bonding pairs, 1 lone pair).
- Electron geometry: Trigonal planar.
- Molecular shape: Bent.
- Bond angle: Slightly less than 120°, due to lone pair repulsion, typically ~115–118° (approximately ~120°).
Final Answers:
| Ion | Shape | Bond Angle |
|---|---|---|
| NO⁻ | Linear | 180° |
| NO₃⁻ | Trigonal planar | 120° |
| NO₂⁻ | Bent | ~120° |
These geometries arise from minimizing electron pair repulsions. Lone pairs repel more strongly than bonding pairs, distorting ideal angles slightly, as seen in NO₂⁻. Resonance also plays a role, especially in NO₃⁻, where the structure is delocalized.
