Occurrence of Metals

📚 Key Concepts

🔹 Real-Life Example

Gold prospectors pan for gold flakes in rivers because gold occurs naturally in pure form – it doesn’t react with water or air. But iron ore must be mined and processed in giant furnaces because iron is too reactive to exist freely in nature. The way metals occur in nature directly relates to their position in the reactivity series!

image

🧪 How Metals Occur

🔸 Free State (Native)

  • Metals: Gold, silver, platinum, copper (sometimes)
  • Why: Very low reactivity (bottom of reactivity series)
  • Examples: Gold nuggets, silver deposits, native copper

🔸 Combined State

  • Most metals: Too reactive to exist freely
  • Form compounds with: Oxygen, sulfur, carbon, halogens

🔸 Types of Compounds

  1. Oxides: Most common (oxygen is abundant and reactive)
    • Examples: Fe₂O₃ (hematite), Al₂O₃ (bauxite), CuO
  2. Sulfides: Common for many metals
    • Examples: ZnS (zinc blende), PbS (galena), CuFeS₂ (copper pyrites)
  3. Carbonates: Some metals
    • Examples: CaCO₃ (limestone), MgCO₃ (magnesite)
  4. Halides: Few metals
    • Examples: NaCl (rock salt), KCl (sylvite)

🔍 Important Definitions

  • Mineral: Any naturally occurring substance containing metals or their compounds
  • Ore: A mineral from which metals can be extracted profitably
  • Gangue: Unwanted rocky material mixed with ore