Question

Which of the following molecules has a trigonal planar molecular geometry?

• A. NH₃
• B. BF₃
• C. H₂O
• D. CH₄

Hint:

Use VSEPR notation (AXₙEₘ) where A is the central atom, X is a bonding pair, and E is a lone pair to predict molecular shapes.

Answer 1

The Correct Option is B

To find molecular geometry with VSEPR theory:

1. Determine bonding and lone pairs around the central atom.
2. For NH₃: \[ \text{Nitrogen: 3 bonding pairs, 1 lone pair} \rightarrow \text{trigonal pyramidal (AX₃E)}. \]
3. For BF₃: \[ \text{Boron: 3 bonding pairs, 0 lone pairs} \rightarrow \text{trigonal planar (AX₃)}. \]
4. For H₂O: \[ \text{Oxygen: 2 bonding pairs, 2 lone pairs} \rightarrow \text{bent (AX₂E₂)}. \]
5. For CH₄: \[ \text{Carbon: 4 bonding pairs, 0 lone pairs} \rightarrow \text{tetrahedral (AX₄)}. \]
6. Conclusion: Only BF₃ has a trigonal planar shape.

Therefore, the answer is: \[ \boxed{\text{BF}_3} \]