Answer:The formula for magnesium nitride is [tex]Mg_3N_2[/tex].
Explanation;
The formula of magnesium nitride is given as[tex]Mg_3N_2[/tex]
[tex]3Mg+N_2\rightarrow Mg_3N_2[/tex]
Magnesium forms cation with 2+ charge and nitrogen forms anion with 3- charge.
Hence, by criss-cross method, the compound formed will be [tex]Mg_3N_2[/tex]