What is the electron-pair geometry for N in NO2-?
There are lone pair(s) around the central atom, so the geometry of NO2- is .
The Correct Answer and Explanation is :
The electron-pair geometry for the nitrogen atom (N) in the nitrite ion (NO₂⁻) is trigonal planar. However, there is also one lone pair on the nitrogen, making the molecular geometry bent or V-shaped.
Explanation:
To understand the electron-pair geometry of NO₂⁻, let’s break it down step by step:
- Valence Electrons: Nitrogen (N) has 5 valence electrons, and each oxygen (O) has 6 valence electrons. In NO₂⁻, there is also an additional electron due to the negative charge. Thus, the total number of valence electrons is:
[
5\ (\text{from N}) + 6 \times 2\ (\text{from two O atoms}) + 1\ (\text{from negative charge}) = 18\ \text{valence electrons}
] - Lewis Structure: In the Lewis structure of NO₂⁻, nitrogen is the central atom, and it forms two bonds with the oxygen atoms. One of these bonds is a single bond, and the other is a double bond. Additionally, there is a lone pair of electrons on the nitrogen atom.
- Electron-Pair Geometry: According to VSEPR (Valence Shell Electron Pair Repulsion) theory, the electron-pair geometry is determined by the number of regions of electron density (bonds or lone pairs) around the central atom. Nitrogen has three regions of electron density: two bonding regions (the N-O bonds) and one lone pair of electrons. These three regions of electron density arrange themselves as far apart as possible, leading to a trigonal planar electron-pair geometry.
- Molecular Geometry: The presence of a lone pair changes the molecular geometry. The lone pair exerts more repulsion than the bonding pairs, causing the molecule to adopt a bent shape, rather than maintaining the ideal trigonal planar structure.
In conclusion, the electron-pair geometry for nitrogen in NO₂⁻ is trigonal planar, but the molecular geometry is bent due to the lone pair.