Final answer:
The molecular geometry of the ClO₃⁻ ion is trigonal pyramidal, due to three bonded oxygen atoms and one lone pair on the central chlorine atom.
Step-by-step explanation:
The molecular geometry of the ClO₃⁻ ion can be determined by first considering the electron-pair geometry based on the number of regions of electron density surrounding the central chlorine atom. In this ion, there are three oxygen atoms bonded to chlorine and one additional lone pair of electrons, making a total of four regions of electron density. This corresponds to a tetrahedral electron-pair geometry. However, we must adjust this to account for the lone pair of electrons which occupies more space and can change the molecular geometry. In this case, the molecule adopts a shape that is best described as trigonal pyramidal, which is essentially a tetrahedron with one vertex missing (where the lone pair of electrons is located).