Concept:The presence of a lone pair on a central atom repels the bond pairs, transforming a flat or symmetrical geometry into a 3D distorted shape.
Formula:$$ \text{Type} = \text{AB}_3\text{E} $$
Solution:- A molecule with 3 bonds and 1 lone pair has 4 total electron domains (\( \text{sp}^3 \) hybridization).
- The underlying electron geometry is tetrahedral.
- However, molecular shape only accounts for the visible atoms. The lone pair pushes the three bonded atoms down like the legs of a camera tripod.
- This results in a Trigonal Pyramidal shape (e.g., Ammonia, \( \text{NH}_3 \)).
Why other options are incorrect:- Option A: Occurs with 3 bonds and 0 lone pairs.
- Option B: Occurs with 4 bonds and 0 lone pairs.
- Option D: Occurs with 2 bonds and 0 (or 3) lone pairs.
Quality & Fidelity Assurance:
Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.