Balancing charges in ionic formulas

Steps:

• The formula Al₂O₃ indicates 2 aluminum ions and 3 oxide ions.
• Oxygen forms O²⁻ ions in most compounds, providing a total charge of 3 × (-2) = -6.
• For the compound to be neutral, the 2 aluminum ions must provide +6 total charge.
• Thus, each aluminum ion has a +3 charge, giving Al³⁺ and O²⁻.

Why C is correct:

• Charges balance as required by ionic compound neutrality: 2(Al³⁺) + 3(O²⁻) = +6 - 6 = 0.

Why the others are wrong:

• A: Charges do not balance: 2(+1) + 3(-1) = -1 ≠ 0.
• B: Charges do not balance: 2(+2) + 3(-2) = -2 ≠ 0.
• D: Charges do not balance: 2(+3) + 3(-1) = +3 ≠ 0.

Final answer: C