Final answer:
The BrF3 anion has a T-shaped molecular geometry, originating from a trigonal bipyramidal structure with LP-BP repulsions influencing the bond angles.
Step-by-step explanation:
The shape of the BrF3 anion is best described as T-shaped. This shape arises from a trigonal bipyramidal electron geometry where two equatorial positions are occupied by lone pairs, leaving the three bromine atoms in a T-shaped arrangement. The axial fluorines (Faxial) and the bromine (Br) create an angle that is less than 180° due to the repulsion between lone pairs (LP) and bonding pairs (BP), specifically mentioned as LP-BP repulsions.