Answer:
H2O < NH3 < CCl4 < BCl3
Explanation:
Bond angle of a molecule or an ion can be explained by two concepts which are either by their valence shell electron pair repulsion (VSEPR) model or hybridization.
The VSEPR model determines the total number of electron pairs surrounding the central atom of the species. All the electron pairs will orient themselves in such a way as to minimize the electrostatic repulsions between them. These repulsions hence determine the geometry of the covalent bond angles around the central atom.
Hence; as the number of lone pairs increases from zero to 2 the bond angles diminish progressively.
Hybridization is the mixing and blending of two or more pure atomic orbitals to form two or moe hybrid atomic orbitals which are identical in shape and energy. During the process of formation of these hybrid orbitals, The bonds formed i.e the sigma bond and the pi bond determines the bond angle of such compound.
From the given compounds;
H20 have a bond angle of 104.5°
NH3 have a bond angle of 107°
BCl3 have a bond angle of 120°
CCl4 have a bond angle of 109.5°
thus in an increasing order of bond angle:
H2O < NH3 < CCl4 < BCl3
