What is the correct formula for the compound formed between magnesium and the phosphate ion?

• A. MgPO4
• B. Mg3(PO4)2
• C. Mg(PO4)2
• D. Mg2(PO4)3

Answer: (B)

Verified step by step guidance

1. Identify the charges of the ions involved: magnesium typically forms a Mg^{2+} ion, and the phosphate ion is PO_4^{3-}.
2. Determine the ratio of magnesium ions to phosphate ions needed to balance the total positive and negative charges so that the compound is electrically neutral.
3. Set up the charge balance equation: let the number of Mg^{2+} ions be x and the number of PO_4^{3-} ions be y. The total positive charge is 2x and the total negative charge is 3y. For neutrality, 2x = 3y.
4. Find the smallest whole number ratio of x to y that satisfies 2x = 3y. This ratio is x = 3 and y = 2.
5. Write the formula using the ratio found: 3 magnesium ions and 2 phosphate ions combine to form Mg_3(PO_4)_2.