Here's why:

* Iodate refers to the anion (negatively charged ion) containing iodine in its +5 oxidation state.

* Iodine (I) is in group 17 (halogens) and typically forms anions with a -1 charge.

* Oxygen (O) is in group 16 (chalcogens) and typically forms anions with a -2 charge.

* To balance the charges and form a neutral molecule, three oxygen atoms (3 x -2 = -6) are needed to counter the +5 charge of the iodine atom. This results in the formula IO₃⁻.