Which elements form an ionic compound? Check all the boxes that apply. aluminum and oxygen calcium and aluminum fluorine and oxygen lithium and fluorine

To form ionic compound Metal should react with Non-metal.

aluminum (metal) and oxygen (non-metal)

calcium (metal) and aluminum (metal)

fluorine (non-metal) and oxygen (non-metal)

lithium (metal) and fluorine (non-metal)

So we have 2 choices that give us ionic compounds:

1) aluminum and oxygen

4) lithium and fluorine