Answer
a. The compound would be called lithium nitride, and its empirical formula would be Li$_{3}$N.
b. The compound would be called gallium oxide, and its empirical formula would be Ga$_{2}$O$_{3}$.
c. The compound would be called rubidium chloride, and its empirical formula would be RbCl.
d. The compound would be called barium sulfide, and its empirical formula would be BaS.
Work Step by Step
a. Li (lithium) is an alkali metal and has an oxidation number of 1+ whereas N (nitrogen) is in group 15 and has an oxidation number of 3-. To have a neutral compound, the positive and negative charges must balance one another. We would need three ions of lithium for every nitrogen ion. The compound would be called lithium nitride, and its empirical formula would be Li$_{3}$N.
b. Ga (gallium) is in group 13 and has an oxidation number of 3+ whereas O (oxygen) is in group 16 and has an oxidation number of 2-. To have a neutral compound, the positive and negative charges must balance one another. We would need two ions of gallium for every three oxygen ions. The compound would be called gallium oxide, and its empirical formula would be Ga$_{2}$O$_{3}$.
c. Rb (rubidium) is an alkali metal and has an oxidation number of 1+ whereas Cl (chlorine) is a halogen and has an oxidation number of 1-. To have a neutral compound, the positive and negative charges must balance one another, and that's what we have. The compound would be called rubidium chloride, and its empirical formula would be RbCl.
d. Ba (barium) is an alkaline earth metal and has an oxidation number of 2+ whereas S (sulfur) is in group 16 and has an oxidation number of 2-. To have a neutral compound, the positive and negative charges must balance one another, and they do in this compound. The compound would be called barium sulfide, and its empirical formula would be BaS because in an empirical formula, we find the smallest whole number ratio of atoms for elements in that compound instead of the actual number of atoms in each formula unit of that compound.
