Reactivity Series

Reactivity Series of Metals

  • Metals vary in chemical reactivity, arranged in a reactivity series.
  • Mnemonic: Metal Popeye Sailor Can Make A Zoo In The Land Having Cute Small Giraffes
    • Potassium > Sodium > Calcium > Magnesium > Aluminium > Zinc > Iron > Tin > Lead > (Hydrogen) > Copper > Silver > Gold

Determining Order of Reactivity

  • Determined by:
    • Reactions with cold water
    • Reactions with steam
    • Reactions with dilute hydrochloric acid

Reactions of Metals with Cold Water

  • General Equation: metal + water → metal hydroxide + hydrogen
    • Potassium: 2K + 2H2O → 2KOH + H2 (explosive)
    • Sodium: 2Na + 2H2O → 2NaOH + H2 (violent)
    • Calcium: Ca + 2H2O → Ca(OH)2 + H2 (readily)
    • Magnesium: Mg + 2H2O → Mg(OH)2 + H2 (slow)
    • Zinc, Iron, Lead, Copper: No reaction

Reactions of Metals with Steam

  • General Equation: metal + steam → metal oxide + hydrogen
    • Calcium: Ca + H2O → CaO + H2 (violent)
    • Magnesium: Mg + H2O(g) → MgO + H2 (vibrant white glow)
    • Zinc: Zn + H2O(g) → ZnO + H2 (only hot zinc)
    • Iron: 3Fe + 4H2O → Fe3O4 + 4H2 (slow, requires heat)

Reactions of Metals with Acids

  • General Equation: metal + acid → salt + hydrogen
    • Potassium: 2K + 2HCl → 2KCl + H2 (explosive)
    • Sodium: 2Na + 2HCl → 2NaCl + H2 (explosive)
    • Calcium: Ca + 2HCl → CaCl2 + H2 (violent)
    • Magnesium: Mg + 2HCl → MgCl2 + H2 (rapid)
    • Zinc: Zn + 2HCl → ZnCl2 + H2 (moderate)
    • Iron: Fe + 2HCl → FeCl2 + H2 (slow)

Reduction of Metal Oxides

  • More reactive metals have stable metal oxides; reduction attempts convert metal oxides back to metal.
  • Reactions:
    • With carbon: Metal oxide + carbon → metal + CO2
    • With hydrogen: Metal oxide + hydrogen → metal + steam

Corrosion and Rusting of Iron

  • Rusting requires: air (oxygen) and water.
  • Prevent rusting via:
    • Surface Barrier Protection (painting, greasing)
    • Sacrificial Protection (using zinc or magnesium)

Extraction of Metals

  • Extraction depends on metal reactivity:
    • Most reactive (K, Na, Ca): Electrolysis
    • Middle reactive (Mg, Zn, Fe): Reduction with carbon
    • Least reactive (Cu, Ag, Au): Found uncombined, extracted physically

Summary of Reactivity Series

  • Higher reactivity means:
    • Greater tendency to lose electrons, and form positive ions.
    • A more reactive metal displaces a less reactive metal in reactions of a salt solution.