Final answer:
The charge on the iron in iron (III) chloride must be +3 to balance the 3- charge from the three chloride ions, ensuring the net charge of the compound is zero.
Step-by-step explanation:
The student asked about the charge on iron in iron (III) chloride, given that the sum of charges within the compound must equal zero. It's important to clarify that iron (III) implies that iron has a +3 oxidation state, and since each chloride ion has a 1- charge, three chloride ions will accumulate a total negative charge of 3-. Therefore, to balance the charges and achieve a net charge of zero, the iron ion must have a +3 charge.
In iron (III) chloride, which can be denoted as FeCl3, there must be one iron ion with a +3 charge for every three chloride ions, each with a -1 charge. This ensures that the compound remains electrically neutral. For instance, in a crystal of iron (III) chloride, there are indeed three times as many chloride ions (Cl-) as there are iron (III) ions (Fe3+).