Answer:
The empirical formulas for four ionic compounds that could be formed from the given ions:
Iron(II) chloride: Fe2+ + 2Cl- → FeCl2
Iron(III) oxide: 2Fe3+ + 3O2- → Fe2O3
Chromium(IV) chloride: Cr4+ + 4Cl- → CrCl4
Chromium(IV) oxide: 2Cr4+ + 3O2- → Cr2O3