The shape of molecule is the particular arrangement of electron pairs around the central atom. VSEPR stands for valence shell electron pair repulsion theory.

Shape of molecule containing bond pairs and lone pairs

The regular shape of the molecule got distorted due to the presence of lone pair. The order of repulsion varies in this manner L.P. – L.P. > L.P. – B.P. > B.P. -B.P.

Shape of NH3 molecule

1. In NH3 there are 3 bond pairs and 1 lone pair.
2. The regular tetrahedron bond angle reduces from 109.28 degree to 107 degrees.
3. The decrease in bond angle is due to bond pair-lone pair repulsion.
4. The shape of the molecule is trigonal pyramidal.

Shape of H2O molecule

1. In H2O there are 2 bond pairs and 2 lone pairs.
2. The regular tetrahedron bond angle reduces from 109.28 degree to 104.5 degrees.
3. The decrease in bond angle is due to lone pair – lone pair repulsion and bond pair – bond pair repulsion.
4. Hence due to greater repulsions in H2O, the bond angle reduces from 109.28 degree to 104.5 degrees.
5. H2O is bent or V shaped molecule.

Shape of SF4 molecule

1. In SF4, Sulphur has 5 bond pairs ( 4 bond pairs + 1 lone Pair )
2. Hence, the arrangement is trigonal bipyramidal.
3. There are 3 lone pair-bond pair repulsions at 90 degree in structure (a)
4. There are only 2 lone pair-bond pair repulsions at 120 degree in structure (b)
5. The distorted shape becomes see saw.

Shape of ClF3 molecule

1. In ClF3 molecule, based on lp-lp , lp-bp and bp-bp repulsions, the least repulsions are there when lone pairs are present at equatorial position.
2. Therefore, the molecule will acquire T shape.
3. Because in SF4 the lone pairs present at equatorial position repel the bond pairs present at axial position.

Check out the post on VSEPR part 1 here :

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