Based on rigorous VSEPR theory incorporating lone-pair repulsions, what is the exact number of perfe — Chemical Bonding Chemistry Question

💡 Solution & Explanation

$BrF_5$ is $sp^3d^2$ hybridized with 5 bond pairs and 1 lone pair, adopting a square pyramidal geometry. Because the single lone pair situated below the basal plane exerts greater repulsion ($lp-bp > bp-bp$) on the four equatorial $Br-F$ bonds, they are pushed upward toward the axial fluorine. Consequently, all adjacent $F-Br-F$ angles shrink to slightly less than $90^\circ$ (approx $84.8^\circ$), leaving exactly 0 angles at a perfect $90^\circ$.