What is the correct name for the ionic compound Mg_3(PO_4)_2?

• A. Magnesium diphosphate
• B. Magnesium phosphate
• C. Magnesium phosphite
• D. Trimagnesium phosphate

Answer: (B)

Verified step by step guidance

1. Identify the cation and anion in the formula \(\mathrm{Mg_3(PO_4)_2}\). Here, \(\mathrm{Mg^{2+}}\) is the cation (magnesium ion) and \(\mathrm{PO_4^{3-}}\) is the anion (phosphate ion).
2. Determine the charges of the ions: magnesium ion has a charge of +2, and phosphate ion has a charge of -3.
3. Check the ratio of ions in the formula to ensure charge neutrality. Three \(\mathrm{Mg^{2+}}\) ions contribute a total charge of \$3 \times (+2) = +6\(, and two \)\mathrm{PO_4^{3-}}\( ions contribute a total charge of \)2 \times (-3) = -6$. The charges balance out, confirming the formula is correct.
4. Name the compound by naming the cation first followed by the anion. The cation \(\mathrm{Mg^{2+}}\) is named 'magnesium' and the anion \(\mathrm{PO_4^{3-}}\) is named 'phosphate'.
5. Combine the names without prefixes because ionic compounds do not use prefixes to indicate the number of ions. The correct name is 'magnesium phosphate'.