The chemical formula for potassium sulfide is K2S.
Explanation: Potassium sulfide is formed from potassium (K) and sulfur (S) elements. Potassium is an alkali metal that typically forms a +1 charge as an ion (K+), while sulfur usually forms a -2 charge (S2-). To balance the charges, two potassium ions are needed to combine with one sulfide ion. This results in the formula K2S, indicating that there are two potassium atoms for every sulfide ion in the compound.