Concept:The central Oxygen atom in a water molecule is \( \text{sp}^3 \) hybridized, containing an octet of electrons made up of both shared and unshared pairs.
Formula:$$ \text{Total Pairs} = \text{Bond Pairs (BP)} + \text{Lone Pairs (LP)} $$
Solution:- Oxygen (Group 6) has 6 valence electrons.
- It shares 2 of these electrons with 2 Hydrogen atoms to form 2 single covalent bonds (2 bond pairs).
- This leaves 4 electrons unshared, which group together as 2 lone pairs.
- Total electron pairs = 2 (BP) + 2 (LP) = 4 pairs.
Why other options are incorrect:- Option A: This is only the number of bond pairs, ignoring the lone pairs.
- Option B & Option D: Represent incorrect valence counts (e.g., Ammonia has 4 pairs total, not 3. \( \text{PCl}_5 \) has 5).
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.