The molecular geometry of BrO4 (bromate ion) is tetrahedral.
To understand why BrO4 has this shape, we can look at the structure and hybridization of the bromine atom in the ion. Bromine is the central atom and is bonded to four oxygen atoms. In order for bromine to accommodate these four bonds, it undergoes sp3 hybridization, forming four equivalent hybrid orbitals.
According to VSEPR (Valence Shell Electron Pair Repulsion) theory, the repulsion between these four bonding pairs will arrange them as far apart as possible, resulting in a tetrahedral shape. There are no lone pairs on the bromine atom in BrO4, which further confirms this geometry.
In conclusion, the BrO4 ion exhibits a tetrahedral molecular geometry due to the sp3 hybridization of bromine and the arrangement of its four equivalent bonds with oxygen.