Nitrogen can ionically bond with an unknown element x from group 2. how many ions of element x are required to create a stable ionic compound with nitrogen?
question 15 options:
2
03
4
there is not enough information

I can tell you there certainly is enough information, so we can eliminate the fourth option right away.
Group two elements tend to form 2+ cations, and nitrogen forms 3- anions. To make a stable substance, we need those to cancel out. Calling the group 2 element X:
N2X3 would cause the charge to be 2(-3) + 3(2) = 0
This would mean 3 ions of X and 2 anions of N would be a stable ionic compound.