20.0 METALS (EXTRACTION AND PROPERTIES)

Metals have shaped human civilization – from the Bronze Age to the Iron Age to the modern age of aluminium and alloys. This chapter explores how we extract metals from their ores, focusing on the relationship between reactivity and extraction method. We examine the extraction of sodium, aluminium, iron, copper, zinc, and lead, and conclude with the properties and uses of important alloys like steel, brass, and bronze.

20.1 METHODS OF EXTRACTION

The method used to extract a metal from its ore depends on its position in the reactivity series.

20.1.1 The Reactivity Series

Metals are arranged in order of their reactivity (most reactive first):

• Potassium (K) – most reactive
• Sodium (Na)
• Calcium (Ca)
• Magnesium (Mg)
• Aluminium (Al)
• Zinc (Zn)
• Iron (Fe)
• Tin (Sn)
• Lead (Pb)
• Copper (Cu)
• Silver (Ag) – least reactive (found native)
• Gold (Au) – least reactive (found native)

20.1.2 Extraction by Electrolysis

Metals above carbon in the reactivity series (K, Na, Ca, Mg, Al) are extracted by electrolysis of their molten compounds. These metals are too reactive to be reduced by carbon; they form very stable compounds that require large amounts of energy to break down.

Principle: Passing an electric current through the molten (melted) ore decomposes it into the metal and non-metal.

Examples: Sodium (Dow