PCl5 places phosphorus in the center with five P–Cl single bonds. Phosphorus is a third-period element and is shown with ten electrons around it in the standard expanded-octet Lewis structure.
Five P–Cl single bonds; three lone pairs on each chlorine
Total valence electrons40
Central atomPhosphorus
Molecular geometryTrigonal bipyramidal
Bond angles90° and 120°
PCl5 Lewis structure overview
Phosphorus supplies five valence electrons and the five chlorine atoms supply thirty-five. Five single bonds use ten electrons; the remaining thirty electrons complete the octets of the chlorine atoms. No electrons remain as lone pairs on phosphorus.
How to draw the PCl5 Lewis structure
Count 40 valence electrons.
Add 5 from phosphorus and 7 from each chlorine.
Place phosphorus in the center.
Chlorine is terminal and phosphorus can connect to all five atoms.
Draw five P–Cl bonds.
The bonds use 10 electrons.
Complete chlorine octets.
Add three lone pairs to each chlorine, using the remaining 30 electrons.
Check the central atom.
Phosphorus has ten electrons around it and no formal charge.
Expanded octet and formal charges
The common Lewis model permits phosphorus to exceed eight electrons. With five single bonds, phosphorus and every chlorine have formal charge zero, so no charge-separated alternative is needed.
Geometry and bond positions
Five electron domains produce trigonal bipyramidal geometry: three equatorial bonds are 120° apart, and two axial bonds are perpendicular to the equatorial plane. Axial P–Cl bonds experience more 90° interactions.
Common mistakes
Stopping at four P–Cl bonds and leaving one chlorine disconnected.
Adding a lone pair to phosphorus after all 40 electrons are used.
Calling the geometry tetrahedral or square pyramidal.
Forcing phosphorus to obey an octet by introducing unnecessary multiple bonds or charges.
Frequently asked questions
How many lone pairs are on phosphorus in PCl5?
Phosphorus has no lone pairs in the standard gas-phase Lewis structure.
Why can phosphorus have ten electrons?
Introductory Lewis models allow third-period and heavier elements to form expanded-valence structures.
What is phosphorus's hybridization in PCl5?
Traditional introductory descriptions use sp³d hybridization, although modern bonding treatments are more nuanced.