Reactivity Series

• Reactivity Series:

  • Potassium – most reactive, so most easily forms positive ions
  • Sodium
  • Lithium
  • Calcium
  • Magnesium
  • Aluminium
  • Carbon
  • Zinc
  • Iron
  • Lead
  • Hydrogen
  • Copper – least reactive, so difficulty forming positive ions
  • Silver
  • Gold
  • Platinum
• Metals are arranged on the reactivity series according to their ability to lose electrons.
• The reactivity of a metal is linked to how easy it is for a metal to form its positive ion. The reactivity series of metals is a chart showing metals in order of decreasing reactivity. In general, the more reactive a metal is the more vigorous its reactions are.
• A metal that is higher up the reactivity series will displace a metal lower down from an aqueous solution of one of its salts.
• In general, the more reactive a metal is the more vigorous its reactions are.
• ​

  Gold and platinum are examples of highly unreactive metals. These metals are found in the Earth’s crust as pure metals. We call them native metals.
• When reacting with other substances, metal atoms always form positive ions.
• The more reactive a metal, the more easily it loses electrons to form a positive ion.
• When a metal reacts with water, a metal hydroxide and hydrogen are formed.
• When a metal reacts with a dilute acid, a salt and hydrogen are formed.
• The more reactive the metal, the more rapid the reaction is. A metal below hydrogen in the reactivity series will not react with dilute acids.    ​

  Hydrogen is always made when a metal reacts with water or a dilute acid.
• A more reactive metal can displace a less reactive metal from its compounds. 
• If the metal is less reactive than the metal in the compound, it will not compete and so there is no reaction.
• Many metals react with oxygen to make metal oxides.
• ​

  The reactions are oxidation reactions because the metal gains oxygen.

  ​

  Oxidation is the gain of oxygen. Reduction is the loss of oxygen. 
• If reduction and oxidation are going on side-by-side, this is known as a redox reaction.
• An oxidising agent is a substance which oxidises something else.
• ​

  A reducing agent reduces something else.
• An ore is a rock that contains enough of a metal or a metal compound to make extracting the metal worthwhile.​
• The extraction method used depends upon the metal's position in the reactivity series. In principle, any metal could be extracted from its compounds using electrolysis. However, large amounts of electrical energy are needed to do this, so electrolysis is expensive.
• If a metal is less reactive than carbon, it can be extracted from its compounds by heating with carbon. Copper is an example of this. Copper mostly occurs as sulfide ores, which are heated in air to convert them to copper(II) oxide. Molten copper can be produced from copper oxide by heating with carbon.
• Extracting a metal by heating with carbon is cheaper than using electrolysis.
• Iron is extracted from iron ore in a huge container called a blast furnace. Iron ores such as haematite contain iron(III) oxide, Fe2O3. The oxygen must be removed from the iron(III) oxide in order to leave the iron behind. Reactions in which oxygen is removed are called reduction reactions.
• The Earth's supply of metal ores is limited. For example, high-grade copper ores, which contain a high percentage of copper, are becoming harder to find and mine. There are some alternative methods to extract metals from low-grade copper ores that use living organisms.
• Phytoextraction (phytomining)​

  Plants absorb mineral ions through their roots. Phytoextraction makes use of this:​

  1. plants are grown in soil that contains low grade ore​
  2. the plants absorb metal ions through their roots and concentrate these ions in their cells​
  3. the plants are harvested and burnt​
  4. the ash left behind contains metal compounds
• Phytoextraction is slow but it:​

  • reduces the need to obtain new ore by mining​
  • conserves limited supplies of high-grade ores​
  • reduces the amount of rock waste that must be disposed of after traditional mining​
• ​

  Mining for metal ores involves quarries which are large holes in the ground. These create noise, dust and traffic. They also destroy natural habitats. Phytoextraction reduces the need for mining and reduces this damage.
• Bioleaching​

  Certain bacteria can break down low-grade ores to produce an acidic solution containing copper ions. The solution is called a leachate and the process is called bioleaching.​

  Bioleaching does not need high temperatures but it:​

  • produces toxic substances, including sulfuric acid, which damage the environment
• Iron is more reactive than copper. It can displace copper from the leachate. Since iron is cheaper than copper, the use of scrap iron is a cost-effective way to produce copperfrom the leachate.
• Metals can oxidise in air. They react with oxygen and form metal oxides.
• ​

  Corrosion happens when a metal continues to oxidise. The metal becomes weaker over time and eventually all of it may become metal oxide.
• Rusting is an example of corrosion. It occurs when iron or steel reacts with oxygen and water.
• A common process that is used to protect steel products is galvanising. Steel products are given a zinc coating by dipping them into the molten zinc. The zinc corrodes before the steel does, allowing it to last longer.