What is the empirical formula of at least four binary ionic compounds that could be formed from the ions Fe²⁺, Al³⁺, Cl⁻, and S²⁻?

To form binary ionic compounds, we combine cations with anions in a way that the total positive charge equals the total negative charge. Here’s how we can derive the empirical formulas for four compounds using Fe²⁺, Al³⁺, Cl⁻, and S²⁻:

1. Iron(II) Chloride (FeCl₂)
   Combining one Fe²⁺ ion with two Cl⁻ ions balances the charges:
   2(-1) + (+2) = 0
2. Aluminum Chloride (AlCl₃)
   One Al³⁺ ion combines with three Cl⁻ ions, achieving charge balance as follows:
   3(-1) + (+3) = 0
3. Iron(II) Sulfide (FeS)
   Here, one Fe²⁺ ion combines with one S²⁻ ion:
   (-2) + (+2) = 0
4. Aluminum Sulfide (Al₂S₃)
   Two Al³⁺ ions are needed to balance with three S²⁻ ions:
   3(-2) + 2(+3) = 0

In summary, the empirical formulas for the compounds formed are FeCl₂, AlCl₃, FeS, and Al₂S₃.