Potassium (K) is in Group 1 of the periodic table and tends to lose one valence electron to achieve a stable electron configuration. This results in the formation of a positively charged potassium ion (K+).
Sulfur (S) is in Group 16 of the periodic table and tends to gain two valence electrons to achieve a stable electron configuration. This results in the formation of a negatively charged sulfide ion (S2-).
To form a neutral compound, the positive and negative charges of the ions must balance. In this case, one potassium ion (K+) with a +1 charge will combine with one sulfide ion (S2-) with a -2 charge.
Therefore, the formula of the ionic compound expected to form between potassium and sulfur is K2S, representing one molecule that contains two potassium ions and one sulfide ion, resulting in a neutral compound.
