Answer:
a) the element belongs to group 2
b) see image attached
c) Magnesium
d) X3N2
Explanation:
Any ion with the formula X^2+ was derived from group 2 elements. The group two element found in period 3 is magnesium alone.
Since the nitride ion has a valency of -3 and X^2+ has a valency of +2 , then a compound formed between X^2+ and the nitride ion will have the formula X3N2.