The Reactivity Series of Metals (Oxford AQA IGCSE Combined Science Double Award)

The Reactivity Series of Metals

The Reactivity Series

• 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

The Reactivity Series

Reactivity 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:

calcium + water → calcium hydroxide + hydrogen

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

• Magnesium reacts very slowly with cold water when finely divided

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

Mg       +    H₂O    →  MgO      +      H₂ 

magnesium + water → magnesium oxide + hydrogen

• Titanium is another example of a metal that reacts with water to form the metal oxide and hydrogen

Reactivity with acids

• 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:

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

Fe    +     2HCI    →    FeCl₂    +    H₂

• 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