Electrons Trigonal planar Trigonal pyramidal The Lewis structure of NO2 shows that nitrogen has bonding group(s) and tetrahedral nonbonding group(s). Therefore, it has electron geometry and molecular geometry. For this molecular geometry, the idealized bond angles are 109.5°. The Lewis structure of NO2 shows that nitrogen has bonding group(s) and nonbonding group(s). Therefore, it has electron geometry and molecular geometry. For this molecular geometry, the idealized bond angles are 120° and 180°. The bond angle is predicted to be less than 109.5° because bonding groups are repelled by nonbonding electrons more than by bonding electrons.
The Correct Answer and Explanation is:
To determine the correct electron geometry, molecular geometry, and bond angles for NO₂ (nitrogen dioxide), we must analyze its Lewis structure and apply VSEPR (Valence Shell Electron Pair Repulsion) theory.
✅ Corrected Answer:
The Lewis structure of NO₂ shows that nitrogen has 2 bonding groups (the two oxygen atoms) and 1 nonbonding group (a lone pair). Therefore, it has trigonal planar electron geometry and bent molecular geometry.
For this molecular geometry, the idealized bond angle is 120°, but the actual bond angle is slightly less than 120° because lone pairs exert greater repulsion than bonding pairs.
🔍 Detailed Explanation
Nitrogen dioxide (NO₂) is a small molecule made up of one nitrogen atom and two oxygen atoms. To understand its geometry, we begin by drawing the Lewis structure. Nitrogen is the central atom, forming one double bond and one single bond with two oxygen atoms, with an odd number of total valence electrons (17). This makes NO₂ a radical, which is somewhat unusual and affects its stability and bonding.
In NO₂, nitrogen is surrounded by two bonding pairs and one lone pair of electrons. According to VSEPR theory, this gives nitrogen a total of three regions of electron density, which arrange themselves in a trigonal planar electron geometry to minimize repulsion.
However, because one of those regions is a lone pair, the molecular geometry becomes bent (or angular). Lone pairs repel bonding pairs more strongly than bonding pairs repel each other, which compresses the bond angle. While the ideal bond angle for a trigonal planar arrangement is 120°, the actual bond angle in NO₂ is slightly less than 120°, typically around 115–118°.
Some confusion arises when comparing this to tetrahedral geometries, which have bond angles of 109.5°. That value applies to molecules with four regions of electron density (e.g., ammonia, NH₃). NO₂, with only three regions, does not fall into this category.
Thus, the correct classification for NO₂ is:
- Electron geometry: Trigonal planar
- Molecular geometry: Bent
- Bond angle: Slightly less than 120°
This understanding helps predict molecular shape and polarity, both critical in chemistry and chemical reactivity.
