Numford
Hybridisation

Hybridisation of H₂O

O is sp³ hybridised (hybridization by the VSEPR count): 2 sigma bonds and 2 lone pairs give a bent shape, bond angle 104.5°.

HOH
  • O
  • H
  • lone pair

H₂OWater

Bent

AB₂E₂: 2 bond pairs, 2 lone pairs

  • Hybridisationsp³
  • Bond angle104.5°
  • Polaritypolar

Why this shape

  1. O has 6 valence electrons. It uses two in two single bonds to H, so four are left as two lone pairs.
  2. Steric number = two sigma bonds + two lone pairs = 4, so O is sp³ hybridised.
  3. Four electron pairs point to the corners of a tetrahedron (tetrahedral electron geometry). With two lone pairs in place of atoms, the atoms make a bent shape.
  4. Repulsion falls in the order lone pair to lone pair > lone pair to bond pair > bond pair to bond pair. The lone pairs push the bond pairs closer, so the angle is 104.5°, less than the ideal 109.5°.
  5. The bond dipoles do not cancel in the bent shape, so H₂O is polar.

Lewis structure

8 valence electrons
OHH

Formal charges: none

Working

Why this hybridisation and shape

  1. O has 6 valence electrons. It uses two in two single bonds to H, so four are left as two lone pairs.
  2. Steric number = two sigma bonds + two lone pairs = 4, so O is sp³ hybridised.
  3. Four electron pairs point to the corners of a tetrahedron (tetrahedral electron geometry). With two lone pairs in place of atoms, the atoms make a bent shape.
  4. Repulsion falls in the order lone pair to lone pair > lone pair to bond pair > bond pair to bond pair. The lone pairs push the bond pairs closer, so the angle is 104.5°, less than the ideal 109.5°.
  5. The bond dipoles do not cancel in the bent shape, so H₂O is polar.

Class 11, Chapter 4 Chemical Bonding and Molecular Structure.

Questions

Hybridisation of H2O: quick answers

What is the hybridisation of H2O?

O has 6 valence electrons. It uses two in two single bonds to H, so four are left as two lone pairs. Steric number = two sigma bonds + two lone pairs = 4, so O is sp³ hybridised.

What is the shape of H2O and its bond angle?

Bent, with a bond angle of 104.5 degrees. Four electron pairs point to the corners of a tetrahedron (tetrahedral electron geometry). With two lone pairs in place of atoms, the atoms make a bent shape. Repulsion falls in the order lone pair to lone pair > lone pair to bond pair > bond pair to bond pair. The lone pairs push the bond pairs closer, so the angle is 104.5°, less than the ideal 109.5°.

Is H2O polar or non-polar?

Polar. The bond dipoles do not cancel in the bent shape, so H₂O is polar.

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