question_answer

In \[Br{{F}_{3}}\] molecule, the lone pairs occupy equatorial positions to minimize:               [AIPMT (S) 2004]

A)  lone pair-bond pair repulsion only

B)  bond pair-bond pair repulsion only

C)  lone pair-lone pair repulsion and lone pair-bond pair repulsion

D)  lone pair-lone pair repulsion only

Correct Answer: C

Solution :

In \[Br{{F}_{3}}\] molecule, Br is \[s{{p}^{3}}\] d-hybrid, but geometry is T-shaped due to distortion of geometry from trigonal-bipyramidal to T-shaped by the involvement of lone pair-lone pair repulsion. Here

\[{{l}_{p}}-{{l}_{p}}\] repulsion = 0

\[{{l}_{p}}-{{b}_{p}}\] repulsion = 4

\[{{b}_{p}}-{{b}_{p}}\] repulsion = 2