Which of the following is the correct formula for the ionic compound formed between Na^+ and PO_4^{3-} ions?

• A. Na_2PO_4
• B. NaPO_3
• C. NaPO_4
• D. Na_3PO_4

Answer: (D)

Verified step by step guidance

1. Identify the charges of the ions involved: sodium ion (Na^+) has a charge of +1, and phosphate ion (PO_4^{3-}) has a charge of -3.
2. Determine the ratio of ions needed to balance the total positive and negative charges so that the compound is electrically neutral.
3. Since each Na^+ ion contributes +1 charge, and the phosphate ion has a -3 charge, you need three Na^+ ions to balance one PO_4^{3-} ion.
4. Write the formula by placing the number of each ion as subscripts: three sodium ions and one phosphate ion, resulting in Na_3PO_4.
5. Confirm that the total positive charge (+3 from 3 Na^+) balances the total negative charge (-3 from 1 PO_4^{3-}), ensuring the compound is neutral.