Magnesium has a charge of +2, and chlorine has a charge of –1. To form a chemical bond, how many magnesium ion(s) would the compound have?

A compound must have an overall charge of zero. One magnesium ion has a +2 charge, which is balanced by two chlorine ions, each with a −1 charge. So the compound contains 1 magnesium ion; the correct choice is B, 1.

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