Numford
Hybridisation

Hybridisation of PCl₃

P is sp³ hybridised (hybridization by the VSEPR count): 3 sigma bonds and 1 lone pair give a trigonal pyramidal shape, bond angle about 100°.

ClClPCl
  • P
  • Cl
  • lone pair

PCl₃Phosphorus trichloride

Trigonal pyramidal

AB₃E: 3 bond pairs, 1 lone pair

  • Hybridisationsp³
  • Bond angleabout 100°
  • Polaritypolar

Why this shape

  1. P has 5 valence electrons. It uses three in three single bonds to Cl, so two are left as one lone pair.
  2. Steric number = three sigma bonds + one lone pair = 4, so P is sp³ hybridised.
  3. Four electron pairs point to the corners of a tetrahedron (tetrahedral electron geometry). With one lone pair in place of atoms, the atoms make a trigonal pyramidal shape.
  4. Repulsion falls in the order lone pair to lone pair > lone pair to bond pair > bond pair to bond pair. The lone pair pushes the bond pairs closer, so the angle is about 100°, less than the ideal 109.5°.
  5. The bond dipoles do not cancel in the trigonal pyramidal shape, so PCl₃ is polar.

Lewis structure

26 valence electrons
PClClCl

Formal charges: none

Working

Why this hybridisation and shape

  1. P has 5 valence electrons. It uses three in three single bonds to Cl, so two are left as one lone pair.
  2. Steric number = three sigma bonds + one lone pair = 4, so P is sp³ hybridised.
  3. Four electron pairs point to the corners of a tetrahedron (tetrahedral electron geometry). With one lone pair in place of atoms, the atoms make a trigonal pyramidal shape.
  4. Repulsion falls in the order lone pair to lone pair > lone pair to bond pair > bond pair to bond pair. The lone pair pushes the bond pairs closer, so the angle is about 100°, less than the ideal 109.5°.
  5. The bond dipoles do not cancel in the trigonal pyramidal shape, so PCl₃ is polar.

Class 11, Chapter 4 Chemical Bonding and Molecular Structure.

Questions

Hybridisation of PCl3: quick answers

What is the hybridisation of PCl3?

P has 5 valence electrons. It uses three in three single bonds to Cl, so two are left as one lone pair. Steric number = three sigma bonds + one lone pair = 4, so P is sp³ hybridised.

What is the shape of PCl3 and its bond angle?

Trigonal pyramidal, with a bond angle of about 100 degrees. Four electron pairs point to the corners of a tetrahedron (tetrahedral electron geometry). With one lone pair in place of atoms, the atoms make a trigonal pyramidal shape. Repulsion falls in the order lone pair to lone pair > lone pair to bond pair > bond pair to bond pair. The lone pair pushes the bond pairs closer, so the angle is about 100°, less than the ideal 109.5°.

Is PCl3 polar or non-polar?

Polar. The bond dipoles do not cancel in the trigonal pyramidal shape, so PCl₃ is polar.

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