The Foundations of Chemistry

The two axial bond dipoles cancel each other, and the three equatorial bond dipoles cancel,

so PF 5 molecules are nonpolar.

C. Valence Bond Theory

Because phosphorus is the central atom in a PF 5 molecule, it must have available five half-

filled orbitals to form bonds with five F atoms. Hybridization involves one dorbital from

the vacant set of 3dorbitals along with the 3sand 3porbitals of the P atom.

P F

F

F

2.1 4.0 P

1.9



(EN) 

EN

FF

F

P

axial bonds equatorial bonds

180 

120 

The two axial bonds are in a linear
arrangement, like the two bonds in
BeCl 2 (see Section 8-5); the three
equatorial bonds are in a trigonal
planar arrangement, like the three
bonds in BF 3 (see Section 8-6).

332 CHAPTER 8: Molecular Structure and Covalent Bonding Theories

3 p

3 d 3 d

sp^3 d

3 s

P[Ne] hybridize P[Ne]

The five sp^3 dhybrid orbitalson P point toward the corners of a trigonal bipyramid. Each

is overlapped by a singly occupied 2porbital of an F atom. The resulting pairing of P and

F electrons forms five covalent bonds.

F

P

F

F

F

sp^3 d hybrid orbitals on P

p orbitals on F

F