To determine the correct formula and name of the compound formed when a \( \text{Mn}^{2+} \) cation combines with a \( \left( \text{PO}_4 \right)^{3-} \) anion, we need to consider the charges on each ion and balance them to form a neutral compound.
1. Identify the charges of the ions:
- The manganese ion \(\text{Mn}^{2+}\) has a charge of \(+2\).
- The phosphate ion \(\left( \text{PO}_4 \right)^{3-}\) has a charge of \( -3 \).
2. Determine the ratio of ions needed to balance the charges:
- To balance the positive and negative charges, we need to find the least common multiple of 2 and 3, which is 6.
- To achieve a total positive charge of \( +6 \) from the manganese ions, we need \(3 \, \text{Mn}^{2+}\) ions (\( 3 \times +2 = +6 \)).
- To achieve a total negative charge of \( -6 \) from the phosphate ions, we need \(2 \, \left( \text{PO}_4 \right)^{3-} \) ions (\( 2 \times -3 = -6 \)).
3. Combine the ions in the correct ratio:
- The formula for the compound that balances the charges is \(\text{Mn}_3\left( \text{PO}_4 \right)_2\).
4. Name the compound:
- This compound is composed of manganese (Mn) and phosphate (\( \text{PO}_4 \)).
- The name of the compound is manganese phosphate.
Therefore, the correct answer is:
A. manganese phosphate: [tex]\(\text{Mn}_3\left( \text{PO}_4 \right)_2\)[/tex]
