The ratio of lithium to nitrogen in an ionic compound is 3:1. Here's why:

* Lithium (Li) is in group 1 of the periodic table, making it a +1 cation (Li⁺).

* Nitrogen (N) is in group 15, making it a -3 anion (N³⁻).

To form a neutral compound, the charges must balance. This requires three lithium ions (3 x +1 = +3) to balance the charge of one nitrogen ion (-3).

Therefore, the formula for the ionic compound is Li₃N.