What is the charge of the iron ion in the following ionic compound: Fe3(PO4)2?
The correct answer and explanation is:
The charge of the iron ion (Fe) in the ionic compound Fe₃(PO₄)₂ is +3.
To explain this, the compound Fe₃(PO₄)₂ consists of iron ions and phosphate ions. Phosphate, PO₄³⁻, is a polyatomic ion with a charge of -3. Since there are two phosphate ions in the formula, their combined charge will be 2 × (-3) = -6.
Now, the iron ions must balance the total negative charge from the phosphate ions. There are three iron ions in the compound, so to balance the -6 charge from the phosphate ions, the total positive charge from the iron ions must be +6.
Since the positive charge from the three iron ions must equal +6, the charge on each iron ion must be +3. Therefore, the charge on the iron ion in this compound is +3.
Thus, the formula Fe₃(PO₄)₂ can be understood as consisting of three Fe³⁺ ions and two PO₄³⁻ ions, ensuring that the overall charge of the compound is neutral. This is how ionic compounds maintain charge balance: the total positive charge from the cations (in this case, iron) exactly cancels out the total negative charge from the anions (in this case, phosphate).