Final answer:
The compound containing an ion with a 3+ charge is FeCl3, which has the iron(III) or ferric ion with a 3+ charge.
Step-by-step explanation:
The student asked which one of the following compounds contains an ion with a 3+ charge. Among the options provided (A) CuCl, (B) MgCl2, (C) Na2O, (D) FeCl3, and (E) KCl, the compound containing an ion with a 3+ charge is FeCl3.
Iron (Fe) can exhibit more than one ionic charge, but in the compound FeCl3, the iron(III) or ferric ion has a 3+ charge to balance the three chloride ions, each of which has a 1- charge. This answers the student's question directly, with a clear example of the ion that has a 3+ charge.