Deduce the molecular shape of BrF3 on the basis of VSEPR theory.
No. of electrons in the valence shell of the central Br atom = 7.
No. of electrons provided by three F atoms = 3 × 1 = 3.
Total no. of electrons around the central Br atom = 10/2 = 5.
Total no. of electron pairs around the central Br atom = 10/2 = 5.
But the no. of bond pairs = 3 (there are three Br—F bonds)
No. of lone pairs = 5 – 3 = 2.
On the basic of VSEPR theory, a molecule with three bond pairs and two lone pair must be T-shaped (i.e., distorted trigonal
bipyramidal) as shown. The two lone pair will occupy equatorial positions to minimize lone pair-lone pair repulsions which are much stronger than lone pair–bond pair repulsions. further, the axial F atoms will be slightly bent towards the equatorial F atom to minimize the lone pair–bond pair repulsions. Therefore, the shape of BrF3 would be slightly bent T as shown in Fig.