Lewis structure of PCl₅
40 valence electrons. Five P-Cl single bonds, with no lone pair on P, so P has 10 electrons around it (an expanded octet).
- P
- Cl
PCl₅Phosphorus pentachloride
Trigonal bipyramidal
AB₅: 5 bond pairs, no lone pairs The two axial P-Cl bonds are longer than the three equatorial ones, because each axial bond pair is 90 degrees from three others. NCERT gives this reason for the high reactivity of PCl5.i
- Hybridisationsp³d
- Bond angle120° and 90°
- Polaritynon-polar
Lewis structure
40 valence electronsFormal charges: none
Why this shape
- P has 5 valence electrons. It uses five in five single bonds to Cl, so none are left over.
- Steric number = five sigma bonds + no lone pairs = 5, so P is sp³d hybridised.
- Five electron pairs point to the corners of a trigonal bipyramid (trigonal bipyramidal electron geometry). With no lone pairs the atoms take the same shape: trigonal bipyramidal.
- All the bond pairs repel each other equally, so the angle is the ideal 120° and 90°.
- The bond dipoles cancel in the symmetric trigonal bipyramidal shape, so PCl₅ is non-polar.
How to draw it
- Count the valence electrons: P 5 + 5 × Cl 7 = 40 valence electrons, 20 pairs.
- Put P in the middle and join it to the five outer atoms with single bonds.
- Give each outer atom lone pairs until it has an octet (H needs only two electrons), then put any electrons left over on the central atom.
- Result: five P-Cl single bonds, with no lone pair on P, so P has 10 electrons around it (an expanded octet).
- Formal charge = valence electrons − lone pair electrons − number of bonds. Here: none.
Class 11, Chapter 4 Chemical Bonding and Molecular Structure.
Lewis structure of PCl5: quick answers
How many valence electrons are in PCl5?
P 5 + 5 × Cl 7 = 40 valence electrons, 20 pairs.
What are the formal charges in the Lewis structure of PCl5?
Every atom has a formal charge of zero.
How many lone pairs are in the Lewis structure of PCl5?
15 in all, none on the central P.