The charges for four ions are sodium (Na) +1, calcium (Ca) +2, fluorine (F) –1, and sulfur (S) –2. Which would be an ionic bond that could form from any of these ions?

An ionic compound must have a total charge of zero. Two sodium ions each have a +1 charge, balancing one sulfur ion with a −2 charge: 2(+1) + (−2) = 0. Therefore, Na₂S, choice B, is a neutral ionic compound. The other formulas either do not balance the listed ion charges or combine two negatively charged ions.

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