Which molecule has a lone pair on the central atom and a pyramidal shape?
Answer and explanation
Correct answer: A.
- Step 1: Evaluate the Lewis valence structure of ammonia (): the central nitrogen atom has five valence electrons, three of which form single covalent -bonds with hydrogen atoms, leaving one non-bonding lone pair.
- Step 2: The four electron domains arrange tetrahedrally ( hybridization). Due to lone pair-bonding pair repulsion, the bond angle compresses from to .
- Step 3: Describing the atomic positions alone yields a trigonal pyramidal molecular geometry with the lone pair at the apex.
Answer
.
Why not the others: is a linear molecule with zero lone pairs on the central carbon atom; has three bonding pairs and zero lone pairs on boron, adopting a flat trigonal planar shape; has four bonding pairs and zero lone pairs, forming a regular tetrahedron.
Practise more Chemical bonding.
Free questions with an explanation for every one, and full timed NEET UG mock tests.