Chapter 9: Metals — Part 2

01 The Reactivity Series

The reactivity series arranges metals in order of their tendency to form positive ions by losing outer shell electrons.

• Order (Most to Least): Potassium, Sodium, Calcium, Magnesium, Aluminium, (Carbon), Zinc, Iron, (Hydrogen), Copper, Silver, Gold.
• Mnemonic: "A Posse of Sly Cats Maliciously Admire Clever Zebras In Hiding Copying Slowly and Gradually".

02 Reactions and Predictions

• Water: Potassium reacts violently (lilac flame); Sodium fizzes rapidly; Calcium reacts more slowly and sinks.
• Acids: Metals above hydrogen react with HCl to produce bubbles of hydrogen; the reaction gets slower as you move down the series until no reaction occurs for copper, silver, and gold.
• Displacement: A more reactive metal will displace a less reactive metal from its compound.
• Aluminium's Apparent Unreactivity: Although high in the series, aluminium often appears unreactive because it forms a tough, unreactive layer of aluminium oxide (Al₂O₃) that prevents further oxidation.

03 Corrosion of Metals (Rusting)

• Rusting is an oxidation reaction that occurs only in the presence of both water and oxygen.
• Chemical Name: Rust is hydrated iron(III) oxide.
• Barrier Methods: Rusting is prevented by excluding oxygen and water using painting, greasing, oiling, or plastic coating.
• Sacrificial Protection: A more reactive metal (like zinc) is used to protect a less reactive metal (iron). The more reactive metal loses electrons more easily, becoming oxidised instead of the iron.
• Galvanising: Coating iron or steel with zinc provides both a barrier and sacrificial protection.