* Potassium (K): It has one electron in its outermost shell, making it highly reactive. It wants to lose this electron to achieve a stable electron configuration.

* Chlorine (Cl): It has seven electrons in its outermost shell. It wants to gain one electron to achieve a stable configuration.

When potassium and chlorine react, potassium *loses* its outermost electron, and chlorine *gains* that electron. This forms a stable ionic bond, resulting in the compound Potassium Chloride (KCl).