Numford
Hybridisation

Hybridisation of PCl₅

P is sp³d hybridised (hybridization by the VSEPR count): 5 sigma bonds and no lone pairs give a trigonal bipyramidal shape, bond angle 120° and 90°.

ClClClPClCl
  • P
  • Cl

PCl₅Phosphorus pentachloride

Trigonal bipyramidal

AB₅: 5 bond pairs, no lone pairs

i

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.

  • Hybridisationsp³d
  • Bond angle120° and 90°
  • Polaritynon-polar

Why this shape

  1. P has 5 valence electrons. It uses five in five single bonds to Cl, so none are left over.
  2. Steric number = five sigma bonds + no lone pairs = 5, so P is sp³d hybridised.
  3. 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.
  4. All the bond pairs repel each other equally, so the angle is the ideal 120° and 90°.
  5. The bond dipoles cancel in the symmetric trigonal bipyramidal shape, so PCl₅ is non-polar.

Lewis structure

40 valence electrons
PClClClClCl

Formal charges: none

Working

Why this hybridisation and shape

  1. P has 5 valence electrons. It uses five in five single bonds to Cl, so none are left over.
  2. Steric number = five sigma bonds + no lone pairs = 5, so P is sp³d hybridised.
  3. 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.
  4. All the bond pairs repel each other equally, so the angle is the ideal 120° and 90°.
  5. The bond dipoles cancel in the symmetric trigonal bipyramidal shape, so PCl₅ is non-polar.

Class 11, Chapter 4 Chemical Bonding and Molecular Structure.

Questions

Hybridisation of PCl5: quick answers

What is the hybridisation of PCl5?

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.

What is the shape of PCl5 and its bond angle?

Trigonal bipyramidal, with a bond angle of 120 degrees and 90 degrees. 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°.

Is PCl5 polar or non-polar?

Non-polar. The bond dipoles cancel in the symmetric trigonal bipyramidal shape, so PCl₅ is non-polar.

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