In case of molecules made up of three or more atoms, the average angle between the bonded orbitals (i.e., between the two covalent bonds) is known as bond angle q.
Factors affecting bond angle
(i) Repulsion between atoms or groups attached to the central atom may increase or decrease the bond angle.
(ii) In hybridisation as the s character of the s hybrid bond increases, the bond angle increases.
(iii) By increasing lone pair of electron, bond angle decreases approximately by 2.5%.
(iv) If the electronegativity of the central atom decreases, bond angle decreases.
In case the central atom remains the same, bond angle increases with the decrease in electronegativity of the surrounding atom.