Question

Using VSEPR theory, draw the shape of PCl₅ and BrF₅.

Answer 1

In PCl₅ phosphorus is sp³ d-hybrid, so

Five sp³ d-hybrid orbitals are present in p and in these three are attached trigonally with an angle of 120°. and rest two are attached bipyramidically with an angle of 90°. These five sp³ d-hybrid orbitals of p are overlapped with five σ-orbitals of five chlorine atoms on their axes and to form five o-bonds. Thus, the geometry of PCl₅ is trigonally bipyramidal given below. (In it VSEPR-theory is not applicable.)

Five sp³d²-hybrid, orbitals are obtained and these are attached octahedrally. In these one sp³d² -hybrid orbital is already paired, so it does not involved in overlapping. Thus, rest five sp³d²-hybride orbitals are overlapped with five p-orbitals of five  fluorine atoms on their axes but the geometry of BrF₅ is not octahedral because it is distorted from octahedral to square of pyramidal due to involvement of repulsion between lone pair and bond pair electrons.

(₉F = 1s² , 2s² 2p²_x 2p²_y 2p¹_z)