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?
(a) 2 Al³⁺ and 3 Cl⁻
(b) 3 Mg²⁺ and 1 PO₄³⁻
(c) 2 Fe³⁺ and 3 O²⁻
(d) 3 Ca²⁺ and 2 SO₄²⁻
(c) 2 Fe³⁺ and 3 O²⁻
Explanation: In an ionic compound, the total positive charge of the cations must be equal to the total negative charge of the anions, so that the compound is electrically neutral. Given that total positive charge is 6 and is equal to the total negative charge (-6).
On checking each option, the total positive charge from 2 Fe³⁺ ions is (2 × 3) = +6, and the total negative charge from 3O²⁻ ions is (3 × 2) = -6. Both charges balance each other and leads to the formation of the neutral compound Fe₂O₃ (ferric oxide).
