The chemical formula for iron (III) nitrite is Fe(NO₂)₃. Here's how to arrive at that:

* Iron (III): The Roman numeral III indicates that iron has a +3 charge (Fe³⁺).

* Nitrite: The nitrite ion has a -1 charge (NO₂⁻).

To balance the charges, we need three nitrite ions (3 x -1 = -3) for every one iron (III) ion (+3). This gives us the formula Fe(NO₂)₃.