When calcium reacts with nitrogen it forms
A. an ionic compound Ca2N3
B. an ionic compound CaN2
C. a covalent compound N2Ca
D. an ionic compound Ca3N2
E. a covalent compound CaN
Solution: Calcium is a metal and nitrogen is a nonmetal. Therefore, the compound must be ionic. Covalent compounds consist of two or more nonmetals only. To write the correct formula, we must figure out the oxidation number of each element, Ca is 2+ since it is in group 2 on the Periodic Table and N is 3-. Putting the formula together, oxidation numbers become subscripts and get exchanged. We get Ca3N2, Choice D
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