VSEPR theory applied to PF5

Steps:

• Phosphorus in PF5 has 10 valence electrons (5 from P, 5 from F), forming 5 single bonds with no lone pairs on P.
• Central P has 5 bonding pairs, 0 lone pairs, so electron geometry is trigonal bipyramidal.
• Molecular shape matches electron geometry: trigonal bipyramidal.
• Assess properties: bond angles vary, symmetry cancels dipoles, shape is not octahedral.

Why B is correct:

• PF5 follows the formula AX5 (A=central atom, X=ligand) in VSEPR, where the central atom has 5 bonds and no lone pairs.

Why the others are wrong:

• A: Trigonal bipyramidal has axial-equatorial angles of 90° and equatorial-equatorial of 120°, not all 90°.
• C: Molecular symmetry in trigonal bipyramidal shape results in zero net dipole moment.
• D: Octahedral geometry requires 6 electron pairs (AX6), but PF5 has 5.

Final answer: B