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: Trimethylamine Structure.
Trimethylamine is characterized by a nitrogen atom bonded to three methyl groups. This nitrogen atom possesses a lone pair of electrons, resulting in a trivalent compound.
Step 2: Nitrogen Geometry in Amines.
The nitrogen atom in amines generally exhibits a pyramidal geometry. The lone pair of electrons repels the bonding pairs, deviating the geometry from a perfect tetrahedral to a pyramidal shape.
Step 3: Option Evaluation.
- Option 1: Tetrahedral is incorrect due to lone pair repulsion, which dictates a pyramidal structure.
- Option 2: Pyramidal accurately describes the geometry of trimethylamine.
- Option 3: Square planar is not applicable here, as it is associated with sp\(^2\) hybridization.
- Option 4: Triangular is incorrect for amines, which are sp\(^3\) hybridized.
Final Answer: \[\boxed{\text{The correct answer is pyramidal.}}\]