Which of the following statements is FALSE regarding molecular shape and polarity according to the VSEPR model?
A) The F-Br-F bond angles in BrF3 are less than 90°. PF3 and BrF3 have different molecular shapes.
B) PF3 has a net dipole moment.
C) BrF3 has a net dipole moment.
D) The shape of BrF3 is trigonal pyramidal.
E) None
The correct answer and explanation is :
The correct answer is D) The shape of BrF3 is trigonal pyramidal.
Explanation:
To understand why statement D is false, let’s analyze each statement based on the VSEPR (Valence Shell Electron Pair Repulsion) model.
- A) The F-Br-F bond angles in BrF3 are less than 90°. PF3 and BrF3 have different molecular shapes. This statement is true. BrF3 has a T-shaped molecular geometry with bond angles that are indeed less than 90° due to the lone pairs of electrons on the central atom (Br). PF3, on the other hand, has a trigonal pyramidal molecular geometry, which is different from BrF3. Therefore, this part is correct.
- B) PF3 has a net dipole moment. This statement is true. PF3 has a trigonal pyramidal geometry with phosphorus as the central atom and fluorine atoms attached to it. Because of the asymmetric arrangement of the fluorine atoms around the central atom and the electronegativity difference between phosphorus and fluorine, PF3 has a net dipole moment.
- C) BrF3 has a net dipole moment. This statement is true. BrF3 has a T-shaped molecular geometry and is asymmetrical. Since the fluorine atoms are more electronegative than bromine, and the molecular shape does not cancel out the individual dipoles, BrF3 has a net dipole moment.
- D) The shape of BrF3 is trigonal pyramidal. This statement is false. According to the VSEPR model, BrF3 (bromine trifluoride) has a T-shaped molecular geometry, not trigonal pyramidal. The central bromine atom has three bonding pairs and two lone pairs of electrons, which leads to the T-shaped geometry. If it were trigonal pyramidal, it would have one lone pair and three bonding pairs, which is not the case for BrF3.
Conclusion:
The only false statement here is D, as the shape of BrF3 is T-shaped, not trigonal pyramidal.
