Multiple Choice
Which of the following best describes the molecular polarity of BeF_2?
13. Liquids, Solids & Intermolecular Forces
Molecular Polarity
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Which of the following best describes the polarity of the molecule BF_3?
A
BF_3 is a polar molecule because it contains three fluorine atoms.
B
BF_3 is a nonpolar molecule because its trigonal planar geometry causes the dipole moments to cancel.
C
BF_3 is a polar molecule because the B–F bonds are polar and the molecule has a net dipole moment.
D
BF_3 is nonpolar because boron and fluorine have similar electronegativities.
Verified step by step guidance1
Step 1: Identify the molecular geometry of BF_3. BF_3 has three fluorine atoms bonded to a central boron atom with no lone pairs on boron, resulting in a trigonal planar shape.
Step 2: Understand bond polarity. The B–F bonds are polar because fluorine is more electronegative than boron, creating bond dipoles pointing from boron to each fluorine atom.
Step 3: Analyze the symmetry of the molecule. In a trigonal planar geometry, the three B–F bond dipoles are arranged 120° apart, symmetrically around the central atom.
Step 4: Determine the net dipole moment. Because of the symmetrical arrangement, the individual bond dipoles cancel each other out, resulting in no overall dipole moment for the molecule.
Step 5: Conclude the polarity of BF_3. Despite having polar bonds, the molecule is nonpolar overall due to its symmetrical trigonal planar geometry causing dipole cancellation.
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