How many lithium ions are required to bond with one nitrogen ion? why?

Nitrogen ions have a charge of -3
Lithium ions have a charge of +1

The sum of nitrogen ions and lithium ions should = 0, that way the equation is true

An example:
NLi3 —> N + Li3

(-3)+(3(+1)) = 0
-3+3=0
0=0

Equation is true.

so we need 3 Lithium ions to equal 1 nitrogen ion, because 3 Lithium ions are required to make the compound NLi3 neutral.

i hope i could help!! good luck :)