common sources of ion of chromium(II) cation vs iron(III) cation

chromium(II) cation iron(III) cation | common sources of ion

chromium(II) cation | chromium silicide (1 eq) | chromium carbide (1 eq) iron(III) cation | iron phosphide (3:1) (1 eq) | iron(III) sulfate hydrate (2 eq) | iron(III) phosphate tetrahydrate (1 eq) | iron(III) perchlorate hydrate (1 eq) | iron(III) oxalate hexahydrate (2 eq) | iron(III) nitrate nonahydrate (1 eq) | hemin (1 eq) | diironnonacarbonyl (1 eq)