Higher: ionic and half equations

The idea

An ionic equation shows only the ions and substances that react, leaving out spectator ions. For neutralisation: H⁺ + OH⁻ → H₂O. Half equations show electrons gained or lost by one species: Na → Na⁺ + e⁻ (oxidation), Cl₂ + 2e⁻ → 2Cl⁻ (reduction). Both atoms and charges must balance.

1. Write all the ions.
2. Cross out ions that appear unchanged on both sides.
3. Balance atoms and total charge; in a half equation, add electrons to balance the charge.

Watch out Electrons are added to the side that needs more negative charge to balance.