Phosphorus pentachloride (PCl₅) Lewis structure
40 valence electrons, trigonal bipyramidal
Build PCl₅ step by step in the Lewis Structure Generator
What is the Lewis structure of PCl₅?
Phosphorus pentachloride, PCl₅, has 40 valence electrons. Phosphorus is the central atom, joined by five P−Cl single bonds. It carries three lone pairs on each Cl. Every formal charge is zero. P is AX₅: trigonal bipyramidal, with ideal bond angles of 90°, 120° and 180°, and the molecule is nonpolar.
Valence electrons in PCl₅
| Element | Group | Valence electrons | Atoms | Electrons |
|---|---|---|---|---|
| Phosphorus | 15 | 5 | 1 | 5 |
| Chlorine | 17 | 7 | 5 | 35 |
| Total | 40 |
In one line: 5 + 5 × 7 = 40. Each atom brings the valence electrons its group gives it.
How to draw the PCl₅ Lewis structure
- Count the valence electrons. Valence electrons: P 5 and each Cl 7. 5 + 5 × 7 = 40.
- Choose the central atom. P goes in the middle: P is the least electronegative atom other than H, χ 2.19 against 3.16 for Cl.
- Join the atoms with single bonds. Five single bonds use 10 electrons, leaving 40 − 10 = 30.
- Complete the outer atoms. Each outer atom takes enough lone pairs to reach eight: 5 Cl × 6 = 30, leaving 30 − 30 = 0.
- Put the rest on the central atom. Nothing is left, so P gets no lone pair, and P now has 10 electrons round it. That is more than eight, which an atom from period 3 on can hold.
- Make multiple bonds where needed. Every atom already has an octet or more, so no lone pair needs to become a bond.
Lone pairs and formal charges in PCl₅
| Atom | Number | Bonds | Lone pairs | Electrons round it | Formal charge, V − N − B/2 |
|---|---|---|---|---|---|
| P (central) | 1 | five single bonds | 0 | 10 | 5 − 0 − 5 = 0 |
| Cl | 5 | one single bond | 3 | 8 | 7 − 6 − 1 = 0 |
V is the atom’s valence electrons, N its nonbonding electrons and B its bonding electrons. The formal charges add up to 0, the molecule’s overall charge.
Shape and polarity of PCl₅
| Central atom | P |
|---|---|
| VSEPR class | AX₅ |
| Electron geometry | trigonal bipyramidal |
| Molecular geometry | trigonal bipyramidal |
| Ideal bond angles | 90°, 120° and 180° |
| Measured bond angle | 120° |
| Polarity, an estimate | nonpolar |
In a trigonal bipyramidal shape identical bonds cancel exactly.
P has five σ bonds and no lone pairs, five electron domains in all, so its electron geometry is trigonal bipyramidal. With no lone pairs, the molecular geometry is the same.
The VSEPR Molecular Geometry viewer turns the AX₅ shape in 3D, lone pairs included.
The measured angle is the accepted experimental value the VSEPR viewer quotes for this molecule.
Work with PCl₅
- Lewis Structure Generator: PCl₅ built step by step, with every formal charge worked out
- VSEPR Molecular Geometry: every VSEPR shape in 3D, with its bond angles
- All 78 Lewis structures: valence electrons, resonance, shape and polarity in one table