Final answer:
b)(H₂O).
The molecule that has a molecular structure that differs from its electron-pair geometry is water
Step-by-step explanation:
The molecule that has a molecular structure that differs from its electron-pair geometry is water (H₂O) (option b).
The electron-pair geometry of water is tetrahedral because it has four electron pairs (two bonding pairs and two lone pairs) around the central oxygen atom.
However, the molecular structure of water is bent or angular because the two lone pairs repel the bonding pairs, causing the molecule to take on a bent shape.
In contrast, the electron-pair geometry of the other molecules given (NH₃, CH₄, and PCl₃) matches their molecular structures.
NH₃ and CH₄ have a tetrahedral electron-pair geometry and tetrahedral molecular structures, while PCl₃ has a trigonal pyramidal electron-pair geometry and trigonal pyramidal molecular structure.