Draw and state the molecular shape of NH3. State the bond angle in NH3.
The Correct Answer and Explanation is:
Correct Answer:
- Molecular Shape of NH₃: Trigonal pyramidal
- Bond Angle in NH₃: Approximately 107°
Explanation
Ammonia, with the chemical formula NH₃, is a simple molecule composed of one nitrogen atom bonded to three hydrogen atoms. To understand its shape, we can apply the Valence Shell Electron Pair Repulsion (VSEPR) theory. This theory states that electron pairs around a central atom will arrange themselves as far apart as possible to minimize repulsion.
In NH₃, nitrogen is the central atom. It has five valence electrons, and it forms three single covalent bonds with hydrogen atoms. This uses up three of the five electrons, leaving one lone pair of electrons on nitrogen. Therefore, there are four regions of electron density (three bonding pairs and one lone pair) around the nitrogen atom.
According to VSEPR theory, four regions of electron density arrange themselves in a tetrahedral geometry to minimize repulsion. However, since one of these regions is a lone pair (which takes up more space than bonding pairs), the actual molecular shape becomes trigonal pyramidal rather than tetrahedral.
The lone pair pushes the bonding pairs closer together, reducing the bond angle from the ideal tetrahedral angle of 109.5° to about 107°. This smaller bond angle is a direct result of the lone pair’s greater repulsive force.
In a diagram, the nitrogen atom would appear at the center, with three hydrogen atoms arranged in a triangle-like base, and the lone pair positioned above nitrogen. The overall shape looks like a pyramid with a triangular base.
To summarize, NH₃ has a trigonal pyramidal shape due to three bonding pairs and one lone pair on nitrogen. The bond angle is approximately 107°, slightly less than the tetrahedral angle because of the lone pair repulsion.
