# What is the formula for an ionic compound made of barium and nitrogen?

$B {a}_{3} {N}_{2}$
Barium is an alkaline earth metal, and forms $B {a}^{2 +}$ ions; nitrogen is from Group 15, and can form nitride ions, ${N}^{3 -}$.
The salt that forms will be electrostatically neutral, so a formula of $B {a}_{3} {N}_{2}$. Charge is balanced.