The Reactivity Series

• Reactions of Metals with Water:

  • 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
• Reactions of Metals with Acids:

  • 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:

  
• 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  
• Metal Solutions Displacement Table: