Answer is: 2Zn + O₂ → 2ZnO (2Zn²⁺ + 2O²⁻). Unbalanced chemical reaction: Zn + O₂ → ZnO. Zn → Zn²⁺ + 2e⁻ / ×2; 2Zn → 2Zn²⁺ + 4e⁻. 4e⁻ + O₂ → 2O²⁻. Zinc lost two electrons and became Zn²⁺, molecule of oxygen gain four electrons and become 2O²⁻. Multiply first reaction with two to have same number of electrons and put coefficients in chemical reaction.
