Question

You want to design a new ionic compound, where the total positive charge is 6+ and the total negative charge is 6−. Which of the following combinations gives the correct number of ions? 

Options

• 2 Al³⁺ and 3 Cl⁻

• \begin{array}{l} 3\ \mathrm{Mg^{2+}}\ \text{and}\ 1\ \mathrm{PO_4^{3-}} \end{array}

• 2 Fe³⁺ and 3 O²⁻

• \begin{array}{l} 3\ \mathrm{Ca^{2+}}\ \text{and}\ 2\ \mathrm{SO_4^{2-}} \end{array}

Answer 1

2 Fe³⁺ and 3 O²⁻

Explanation:

• Total positive charge: $2 \times (+3) = +6$ (from two $\text{Fe}^{3+}$ ions)
• Total negative charge: $3 \times (-2) = -6$ (from three $\text{O}^{2-}$ ions)