JEE Main · 2024 · 30 Jan 2024 · Shift 2 · Chemical Bonding and Molecular Structure

Bromine in ${\text{BrF}}_5$ has five bonding pairs and one lone pair, giving six electron domains and an octahedral electron geometry ($s{p}^3{d}^2$ hybridisation at Br). The lone pair occupies one vertex of the octahedron, leaving the five fluorine atoms in a square pyramidal arrangement, which is the molecular shape. $[{\text{Ni(CN)}}_4{]}^{2-}$ has four domains and no lone pair on Ni in the complex ($ds{p}^2$), giving square planar geometry, while ${\text{PCl}}_5$ and ${\text{PF}}_5$ each have five bonding pairs and no lone pair, giving trigonal bipyramidal geometry. ${\text{BrF}}_5$ is the square pyramidal species.