Final answer:
Using the VSEPR theory, the ideal molecular geometry for BrF₅ is square pyramidal since it has five bonding regions and one lone pair, resulting in a distorted octahedral shape.
Step-by-step explanation:
The ideal molecular geometry for BrF₅ can be determined using the VSEPR (Valence Shell Electron Pair Repulsion) theory, which states that electron pairs around a central atom will repel each other and occupy positions to minimize this repulsion. Bromine pentafluoride (BrF₅) has a total of six electron regions surrounding the central bromine atom (five bonding regions from the five fluorine atoms and one region from the lone pair of electrons). According to VSEPR theory, if there are six regions of electron density, the electron-pair geometry is octahedral. However, since one of these regions is a lone pair, the lone pair will occupy more space than the bonding pairs, leading to a square pyramidal molecular geometry.
The presence of this lone pair distorts the geometry from an ideal octahedral shape to a square pyramidal shape due to LP-BP (lone pair-bonding pair) repulsions.