Question

The nitrogen atom in amines is trivalent and possess an unshared pair of electrons. The geometry of trimethyl amine is:

• A. Tetrahedral
• B. Pyramidal
• C. Square planar
• D. Triangular

Hint:

Amines with a lone pair of electrons on nitrogen exhibit pyramidal geometry due to the lone pair-bond pair repulsion.

Answer 1

The Correct Option is B

Step 1: The Structure of Trimethylamine.
Trimethylamine is an amine where the nitrogen atom is bonded to three methyl groups. The nitrogen atom has a lone pair of electrons, making the compound trivalent.
Step 2: Geometry of Nitrogen in Amines.
The nitrogen atom in amines typically adopts a pyramidal geometry due to the lone pair of electrons, causing repulsion with the bonding pairs and distorting the geometry from a perfect tetrahedral to pyramidal.
Step 3: Comparison of Options.
- Option 1: Tetrahedral is incorrect as the lone pair causes repulsion, leading to a pyramidal structure.
- Option 2: Pyramidal is the correct geometry for trimethylamine.
- Option 3: Square planar does not apply here as it involves sp\(^2\) hybridization.
- Option 4: Triangular is incorrect for amines as they are sp\(^3\) hybridized.
Final Answer: \[ \boxed{\text{The correct answer is pyramidal.}} \]