Question

A covalent molecule $AB_{3}$ has pyramidal structure. The number of lone pair and bond pair of electrons in the molecule are respectively

• A. 2 and 2
• B. 0 and 4
• C. 3 and 1
• D. 1 and 3

Hint:

Pyramidal = 3 Bonds + 1 Lone Pair (e.g., Ammonia).

Answer 1

The Correct Option is D

Step 1: Geometry
A pyramidal structure ($sp^{3}$ hybridization) typically involves four electron pairs.
Step 2: Bonding
In $AB_{3}$, three 'B' atoms are attached to the central 'A' atom, forming 3 bond pairs.
Step 3: Lone Pair
To achieve the pyramidal shape (like $NH_{3}$), there must be 1 lone pair on the central atom that distorts the tetrahedral arrangement.
Step 4: Conclusion
There is 1 lone pair and 3 bond pairs.
Final Answer: (d)