Ionic Equation
An equation that shows only the ions that actually take part in a reaction — removing the spectator ions. Ionic equations are used for reactions in solution.
Example: The full equation for HCl reacting with NaOH is: H⁺(aq) + Cl⁻(aq) + Na⁺(aq) + OH⁻(aq) → Na⁺(aq) + Cl⁻(aq) + H₂O(l) The ionic equation is: H⁺(aq) + OH⁻(aq) → H₂O(l)
Spectator Ions
Ions that are present in solution during a reaction but do not take part in the actual chemical change. They appear on both sides of the full equation unchanged and are removed when writing the ionic equation.
Example: In the reaction between HCl and NaOH, the Na⁺ and Cl⁻ ions are spectator ions.
IUPAC Nomenclature
The internationally agreed system of naming chemical compounds developed by the International Union of Pure and Applied Chemistry. IUPAC names follow fixed rules based on the elements present and the type of bonding.
Examples: Iron(II) chloride, Iron(III) chloride — the Roman numeral in brackets shows the oxidation state of the metal ion.