Aluminum forms a +3 ion. In order for the formula unit Al₂X₃ to be electrically neutral, the element X must form a _____ ion. Nonmetals in the oxygen column do this. Of these elements, only _____ is a diatomic gas.

a) -3, Oxygen
b) +2, Nitrogen
c) -2, Fluorine
d) +3, Chlorine