Answer:
The answer to your question is letter d) LiS₂
Step-by-step explanation:
Ionic compounds are composed by a metal and a non metal element, so all the formulas in this question are ionic, so we need to check the valences are correct.
a. BaO this formula is correct because Ba has a valence of 2 and O also has a valence of 2, as the valences are the same, we do not write them.
b. Ca₃N₂ this is correct because Ca has a valence of 2 and N has a valence of 3, so we cross the valences to write the formula and we get what is written.
c. KCl This formula is correct, K has a valence of 1 and Cl also has a valence of 1, then we do not write them.
d. LiS₂ This formula is incorrect because Li has a valence of 1 and S has a valence of 2, when we cross then we get Li₂S, and not LiS₂.