ionic compound

 because it contains 

magnesium, a  metal , and nitrogen, a 

nonmetal. Magnesium has 2 valence electrons, meaning it is unstable. To become stable, Magnesium wants to 

lose valence electrons. 

Nitrogen has 5 valence electrons, meaning it is 

stable. Nitrogen wants to 

gain electrons to become stable. When an atom

 of magnesium  loses

 2 electrons, a(n)  atom

 of nitrogen  gains  those 2 electrons. The nitrogen 

atom  now has 7 valence electrons. Magnesium is now stable.  Nitrogen is not. Nitrogen needs  2

 more valence electron(s) to become  stable. 

In order to form a stable 

compound of magnesium nitride, all atoms of magnesium must be stable and all atoms of 

nitrogen must be 

stable. For this to happen, there must be 

7 atoms of  magnesium and  7 atoms of nitrogen. Only then can a stable, 

neutral atom of 

magnesium nitride

 be formed.