Numford
Hybridisation

Hybridisation of SO₂

S is sp² hybridised (hybridization by the VSEPR count): 2 sigma bonds and 1 lone pair give a bent shape, bond angle about 119°.

OSO
  • S
  • O
  • lone pair

SO₂Sulphur dioxide

Bent

AB₂E: 2 bond pairs, 1 lone pair

  • Hybridisationsp²
  • Bond angleabout 119°
  • Polaritypolar

Why this shape

  1. S has 6 valence electrons. In the Lewis structure it makes one double bond to O and one single bond to O and keeps one lone pair, which leaves it a formal charge of +1.
  2. Steric number = two sigma bonds + one lone pair = 3, so S is sp² hybridised. A double or triple bond counts once: only its sigma bond uses a hybrid orbital.
  3. Three electron pairs point to the corners of a flat triangle (trigonal planar electron geometry). With one lone pair 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 pair pushes the bond pairs closer, so the angle is about 119°, less than the ideal 120°.
  5. The bond dipoles do not cancel in the bent shape, so SO₂ is polar.

Lewis structure

18 valence electrons, 2 resonance structures
i

Two resonance structures with octets. It is also often drawn as O=S=O with no charges (expanded octet).

SOO+−
SOO+−

Formal charges: S +1, O −1

Working

Why this hybridisation and shape

  1. S has 6 valence electrons. In the Lewis structure it makes one double bond to O and one single bond to O and keeps one lone pair, which leaves it a formal charge of +1.
  2. Steric number = two sigma bonds + one lone pair = 3, so S is sp² hybridised. A double or triple bond counts once: only its sigma bond uses a hybrid orbital.
  3. Three electron pairs point to the corners of a flat triangle (trigonal planar electron geometry). With one lone pair 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 pair pushes the bond pairs closer, so the angle is about 119°, less than the ideal 120°.
  5. The bond dipoles do not cancel in the bent shape, so SO₂ is polar.

Class 11, Chapter 4 Chemical Bonding and Molecular Structure.

Questions

Hybridisation of SO2: quick answers

What is the hybridisation of SO2?

S has 6 valence electrons. In the Lewis structure it makes one double bond to O and one single bond to O and keeps one lone pair, which leaves it a formal charge of +1. Steric number = two sigma bonds + one lone pair = 3, so S is sp² hybridised. A double or triple bond counts once: only its sigma bond uses a hybrid orbital.

What is the shape of SO2 and its bond angle?

Bent, with a bond angle of about 119 degrees. Three electron pairs point to the corners of a flat triangle (trigonal planar electron geometry). With one lone pair 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 pair pushes the bond pairs closer, so the angle is about 119°, less than the ideal 120°.

Is SO2 polar or non-polar?

Polar. The bond dipoles do not cancel in the bent shape, so SO₂ is polar.

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