What is the correct chemical formula for manganese(VII) arsenide?

• A. MnAs
• B. MnAs_7
• C. Mn_7As_2
• D. Mn_2As_7

Answer: (D)

Verified step by step guidance

1. Identify the oxidation states of the elements involved. Manganese(VII) means manganese has an oxidation state of +7, and arsenide typically has an oxidation state of -3.
2. Write the ions with their charges: Manganese(VII) ion is \( \mathrm{Mn}^{7+} \) and arsenide ion is \( \mathrm{As}^{3-} \).
3. Determine the ratio of ions needed to balance the total positive and negative charges so that the compound is electrically neutral. This means the total positive charge must equal the total negative charge.
4. Set up the charge balance equation: \( 7x = 3y \), where \( x \) is the number of manganese ions and \( y \) is the number of arsenide ions. Find the smallest whole number ratio that satisfies this equation.
5. Write the chemical formula using the ratio found, placing the number of atoms as subscripts after each element symbol, resulting in \( \mathrm{Mn}_2\mathrm{As}_7 \).