Potassium (K) has a charge of +1, and sulfur has a charge of –2. Which best describes the compound they make?

A compound must have a total charge of zero. Two potassium ions, each with a +1 charge, balance one sulfide ion with a –2 charge, so the formula is K₂S. Ionic compounds are named with the metal first and the nonmetal ending in “-ide,” giving potassium sulfide.

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