Question

Identify the correct answer

• A. Three resonance structure can be drawn for ozone
• B. BF₃ has non-zero dipole moment
• C. Dipole moment of NF₃ is greater than that of NH₃
• D. Three canonical forms can be drawn for \(CO^{2-}_3 \)ion

Answer 1

The Correct Option is D

Step 1: Evaluation of BF₃

BF₃ exhibits a planar geometry with symmetrically oriented B-F bonds. Consequently, the bond dipole moments neutralize each other, yielding a zero net dipole moment for the molecule. Therefore, option (1) is incorrect.

Step 2: Comparison of NF₃ and NH₃ Dipole Moments

In NF₃, fluorine's superior electronegativity compared to nitrogen results in bond dipoles that do not cancel, thus producing a non-zero dipole moment for NF₃.

While NH₃ also possesses a non-zero dipole moment, NF₃ has a larger dipole moment attributable to the enhanced electronegativity of fluorine. Accordingly, option (2) is correct.

Step 3: Analysis of Options (3) and (4)

Option (3): The Carbonate Ion (CO₃²⁻)

The carbonate ion (CO₃²⁻) is adequately represented by three resonance structures of equivalent contribution, rendering option (3) correct.

Option (4): The Ozone Molecule (O₃)

The ozone molecule (O₃) is characterized by two principal resonance structures, confirming that option (4) is correct.

Step 4: Final Determination

The accurate selection is: Option (4): Three canonical forms can be depicted for the CO₃²⁻ ion.