According to Valence Shell Electron Pair Repulsion (VSEPR) theory, what is the geometric molecular shape and approximate bond angle of the ammonia molecule (NH₃)?
Answer and explanation
Correct answer: C. trigonal pyramidal, approximately 107°
- Step 1: Central nitrogen atom has 5 valence electrons, forming 3 single N-H bonds and retaining 1 lone pair (steric number = 4). Step 2. The electron pair geometry is tetrahedral. Step 3. Lone pair-bonding pair repulsion compresses the H-N-H bond angles from 109.5° down to 107°, giving a trigonal pyramidal shape. Answer: trigonal pyramidal, approximately 107°. Why not the others: Tetrahedral (109.5°) describes methane (CH₄); trigonal planar (120°) describes BF₃; bent (104.5°) describes water (H₂O) with two lone pairs.
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