The Reactivity Series (AQA GCSE Chemistry)

The reactivity series of metals

• Based on how they react with other substances, a reactivity series can be produced in which the metals are placed in order of their reactivity

• Metal atoms form positive ions by loss of electrons when they react with other substances

• The tendency of a metal to lose electrons is a measure of how reactive the metal is

• A metal that is high up on the series loses electrons easily and is thus more reactive than one which is lower down on the series

• Note that although carbon and hydrogen are non-metals, they are included in the series as they are useful in extracting metals from their oxides by reduction processes

Diagram of the reactivity series of metals

• There are several reactivity series mnemonics to help you remember the order of the metals

• One that we like goes as follows: “Please send lions, cats, monkeys and cute zebras into hot countries signed Gordon”

Reactivity series mnemonic table

You can learn the reactivity series with the help of a silly phrase

Chemical properties of metals

• The chemistry of metals is studied by analysing their reactions with water and dilute acid

Metals reacting with water

Metals reacting with water

• Some metals react with water

• Metals above hydrogen in the reactivity series will react with water

  • For some metals such as iron, the reaction may be very slow

  • For other metals such as the alkali metals, the reaction may be quick and potentially hazardous because of their reactivity

• Metals that react with cold water form a metal hydroxide and hydrogen gas:

metal + water → metal hydroxide + hydrogen

• For example, calcium:

Ca       +    2H₂O     → Ca(OH)₂      +      H₂

calcium + water → calcium hydroxide + hydrogen

• Magnesium reacts very slowly with cold water when finely divided

• Magnesium reacts with gaseous water to form a metal oxide and hydrogen gas:

Mg       +    H₂O     → MgO      +      H₂ 

magnesium + water → magnesium oxide + hydrogen

Reactions of metal with cold water summary table

The Group 1 metals are reactive with water, Group 2 metals are less reactive and other metals are generally unreactive with water

Metals reacting with acids

Metals reacting with acid

• Most metals react with dilute acids such as HCl

• Only the ones below hydrogen in the reactivity series will not react with acids

• When acids and metals react, the hydrogen atom in the acid is replaced by the metal atom to produce a salt and hydrogen gas:

metal + acid → metal salt + hydrogen

• For example iron:

Fe    +     2HCI    →    FeCl₂    +    H₂

iron + hydrochloric acid   →  iron(II)chloride + hydrogen

• In both these types of reactions (water and acids) the metals are becoming positive ions

• The reactivity of the metals is related to their tendency to become an ion

• The more reactive the metal the more easily it becomes an ion (by losing electrons)

Reactions of metal with dilute acid summary table

The Group 1 metals are reactive with water, Group 2 metals are less reactive and other metals are generally unreactive with water

Non-metals in the reactivity series

• Why do non-metals appear in the reactivity series of metals?

• A reactivity series will usually contain the elements carbon and hydrogen

• This is because these elements play different roles in our understanding of the reactions of metals and our ability to predict how metals can be extracted from their ores

• From the reactions with water and acids we have seen that whether a reaction takes place depends on the position of the metal in the reactivity series relative to hydrogen

  • A reaction takes place if the metal is able to displace hydrogen from water or acids

• Carbon is a cheap reducing agent which can be used to remove oxygen from metal oxide ores

  • Placing carbon in the reactivity series allows us to see whether a metal oxide can be reduced or not by carbon

• Metals below carbon can be extracted by heating the oxide with carbon

• Metals higher than carbon have to be extracted by other methods, such as electrolysis

Displacement reactions

• The reactivity of metals decreases going down the reactivity series.

• This means that a more reactive metal will displace a less reactive metal from its compounds

• Two examples are:

  • Reacting a metal with a metal oxide (by heating)

  • Reacting a metal with an aqueous solution of a metal compound

• For example, it is possible to reduce copper(II) oxide by heating it with zinc.

• The reducing agent in the reaction is zinc:

Zn    +     CuO    →    ZnO    +    Cu

zinc + copper oxide → zinc oxide + copper

Metal oxide displacement table

Thermite

• The thermite reaction is a highly exothermic reaction that occurs when iron(III) oxide is reacted with aluminium metal

• As aluminium is more reactive than iron, the iron in iron(III) oxide is displaced 

iron(III) oxide + aluminium → iron + aluminium oxide

Fe₂O₃ + 2Al → 2Fe + Al₂O₃

• The reaction releases so much heat that the iron formed is molten so this process is used in welding and incendiary devices

Displacement reactions between metals & aqueous solutions of metal salts

• The reactivity between two metals can be compared using displacement reactions in salt solutions of one of the metals

• This is easily seen as the more reactive metal slowly disappears from the solution, displacing the less reactive metal

• For example, magnesium is a reactive metal and can displace copper from a copper sulfate solution:

Mg + CuSO₄  →  MgSO₄ + Cu

• The blue colour of the CuSO₄ solution fades as colourless magnesium sulfate solution is formed.

• Copper coats the surface of the magnesium and also forms solid metal which falls to the bottom of the beaker

Diagram showing the colour change when magnesium displaces copper from copper sulfate

Other displacement reactions

Metal solutions displacement table