Question

what is the formula for the ionic compound containing iron(iii) ions and iodide ions?
○ fei
○ fe₂i
○ fei₂
○ fei₃
○ fe₃i

Explanation:

Step1: Determine ion charges

Iron(III) ion is $\text{Fe}^{3+}$, iodide ion is $\text{I}^-$.

Step2: Balance charges

To balance the charges, we need 3 iodide ions (each with -1 charge) to balance the +3 charge of one iron(III) ion. So the formula is $\text{FeI}_3$.

Answer:

$\text{FeI}_3$ (corresponding to the option FeI₃)