Which elements form an ionic compound?Check all the boxes that apply.

Ionic compounds usually form between a metal and a nonmetal: the metal transfers electrons to the nonmetal. Aluminum is a metal and oxygen is a nonmetal, so they can form an ionic compound. Lithium is a metal and fluorine is a nonmetal, so they can form one too. Calcium and aluminum are both metals, while fluorine and oxygen are both nonmetals; those pairs do not form ionic compounds by this rule.

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