The formula for the ionic compound of potassium and iodide is KI. Here's how we get that:

* Potassium (K) is in group 1 of the periodic table, meaning it has a +1 charge as a cation (K⁺).

* Iodine (I) is in group 17 of the periodic table, meaning it has a -1 charge as an anion (I⁻).

Since the charges are equal and opposite, they cancel each other out, resulting in a neutral compound with the formula KI.