Numford
Hybridisation

Hybridisation of O₃

The central O atom is sp² hybridised (hybridization by the VSEPR count): 2 sigma bonds and 1 lone pair give a bent shape, bond angle about 117°.

OOO
  • O
  • lone pair

O₃Ozone

Bent

AB₂E: 2 bond pairs, 1 lone pair on central O

  • Hybridisationsp²
  • Bond angleabout 117°
  • Polaritypolar

Why this shape

  1. The central O 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 the central O 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 117°, less than the ideal 120°.
  5. All three atoms are O, but the central O carries a different charge from the end ones and the molecule is bent, so it has a small dipole moment.

Lewis structure

18 valence electrons, 2 resonance structures
i

NCERT draws these two resonance structures; both O-O bonds are the same length.

OOO+−
OOO+−

Formal charges: O +1, O −1

Working

Why this hybridisation and shape

  1. The central O 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 the central O 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 117°, less than the ideal 120°.
  5. All three atoms are O, but the central O carries a different charge from the end ones and the molecule is bent, so it has a small dipole moment.

Class 11, Chapter 4 Chemical Bonding and Molecular Structure.

Questions

Hybridisation of O3: quick answers

What is the hybridisation of O3?

The central O 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 the central O is sp² hybridised. A double or triple bond counts once: only its sigma bond uses a hybrid orbital.

What is the shape of O3 and its bond angle?

Bent, with a bond angle of about 117 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 117°, less than the ideal 120°.

Is O3 polar or non-polar?

Polar. All three atoms are O, but the central O carries a different charge from the end ones and the molecule is bent, so it has a small dipole moment.

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