The Reactivity Series (OCR Gateway GCSE Chemistry)

• 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 more reactive metal loses electrons more easily than a less reactive one
• Some metals react with water 
• 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

• Most metals react with dilute acids such as HCl
• 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)

The Reactions of Metals with Cold Water and Dilute Acids Summary Table

• The reactions of  metals and acids and metals and water allow them to be put into an order based on their reactivity, known as the reactivity series shown below
• This can be done experimentally by observing the rate of reaction between them
• The more reactive a metal is, the greater the rate of hydrogen production so the reaction will be more vigorous 

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"

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

• A reactivity series will usually contain the non-metal elements carbon and hydrogen
• This is because these elements play different roles in our understanding the reactions of metals and our ability to predict how metals can be extracted from their ores
• Reactions between metals and acids/water take place if the metal is able to displace the hydrogen in them
• 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
• 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  

• Some other examples of displacement reactions can be found in the table below 

Metal Solutions Displacement Table