Final answer:
The correct formula for magnesium phosphate is Mg3(PO4)2, which is achieved by balancing the charges of Mg2+ and PO43- ions to create an electrically neutral compound.
Step-by-step explanation:
The correct formula for magnesium phosphate is Mg3(PO4)2. Magnesium ion has a charge of +2 (Mg2+), and phosphate ion has a charge of -3 (PO43-). When combining these ions to form an electrically neutral compound, we need to balance the charges by finding the least common multiple.
For this, we need three magnesium ions to get a total charge of +6, and two phosphate ions to get a total charge of -6. Thus the correct formula for the compound is Mg3(PO4)2, making the answer (d).