KCl is an ionic compound, and it doesn't have a specific "formula" in the way that covalent molecules do. It's more accurate to describe it as a formula unit.

Here's why:

* Ionic compounds are formed by electrostatic attraction between oppositely charged ions.

* KCl is made up of potassium cations (K+) and chloride anions (Cl-) that are held together in a crystal lattice structure.

* The ratio of potassium to chloride ions is 1:1. This means there is one potassium ion for every chloride ion.

Therefore, the formula unit of KCl is simply KCl. This indicates the ratio of ions in the compound, not a specific molecule.