An ion of calcium has a +2 charge, and an ion of chlorine has a –1 charge.How many chlorine ions are needed to create a stable ionic compound with an ion of calcium?

A calcium ion has a +2 charge, while each chlorine ion has a −1 charge. Two chlorine ions give a total charge of −2, which balances calcium’s +2 charge and makes the compound neutral. Therefore, two chlorine ions are needed.

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