Reactivity and form Extraction of a metal from its ore

Metals are found in many different forms from gold and platinum as pure native metals, through mercury as metal drops in red cinnabar ore, to iron in mountains of iron oxide rust and lithium and sodium as salts in seawater.

Reactivity and form
The form a metal takes in the natural world is dependent on its reactivity with water and air. The inert or unreactive metals like gold and platinum are found as native metals. More reactive metals like mercury and copper can be found as both native metals and as compounds in ores. While the most reactive metals are never found in the metal form, but always as compounds in rock ore or in sea water.

This table shows the reactivity of some common metals, including a section showing how each metal is normally found in nature.

Extraction of a metal from its ore
The more reactive a metal is (i.e. Li, K and Ca) the more difficult it is to extract the metal from its ore or salt.

Although methods of production will vary from one metal to another, depending on their individual relativities and physical properties, the extraction of metals can be divided into four main types:

• The moderate to highly reactive metals, from Li to Zn, are obtained by electrolysis of a salt containing the respective metal. This involves melting the pure salt at high temperature in a large electric cell and passing an electric current through the molten salt. The metal is collected at one electrode and the other elements in the salt collected at the other. See the topic Production of aluminium for more on electrolysis.
  
  The production of sodium metal from salt is demonstrated in the following animation.
  
  

  Downs cell - NaCl electrolysis

• The less reactive metals, from Fe to Cu on the above table, typically are produced by reduction of the ore in a blast furnace with carbon. This involves mixing the crushed ore, usually metal oxides and sulphides, with coal or coke. Lime is added to remove waste material and the whole lot is heated together. See the topic Production of iron for more on this process. The blast furnace animation shows this process in action.
  
  

  Blast furnace

• Mercury and silver are either obtained as native metals or by heating their ores releasing the metal from the ore. In the case of mercury this is a very simple process involving heating cinnabar (red mercury sulphide) and collecting the mercury vapours. This is demonstrated in the following animation.




Heating cinnabar

• Gold and platinum are usually either found as pure native metals or are extracted by separating the metal from their surrounding rock by crushing and dissolving the metal out with strong acids and cyanide solutions. The river pollution from the Ok Tedi mine in Papua New Guinea in 2000 clearly shows the problems associated with this type of mining and extraction process.
  

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