Reactivity Series (Cambridge O Level Chemistry)

• The chemistry of the metals is studied by analysing their reactions with water and acids
• Based on these reactions a reactivity series of metals can be produced
• The series can be used to place a group of metals in order of reactivity based on the observations of their reactions with water and acids
• The non-metals hydrogen and carbon are also included in the reactivity series as they are used to extract metals from their oxides

Table of Metal Reactions

The reactivity series mnemonic

• Observations from the table above allow the following reactivity series to be deduced
• The order of this reactivity series can be memorised using the following mnemonic 
  • “Please send cats, monkeys and cute zebras into hot countries signed Gordon"

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

Reactions of Metals

Reaction with cold water

• The more reactive metals will react with cold water to form a metal hydroxide and hydrogen gas
• Potassium, sodium and calcium all undergo reactions with cold water as they are the most reactive metals:

metal + water →  metal hydroxide + hydrogen

•  For example, calcium and potassium:

Ca (s) + 2H₂O (l) → Ca(OH)₂ (aq) + H₂ (g)

K (s) + H₂O (l) → KOH (aq) + H₂ (g)

Reaction with steam

• Metals just below calcium in the reactivity series do not react with cold water but will react with steam to form a metal oxide and hydrogen gas, for example, magnesium:

Mg (s) + H₂O (g)  →  MgO (s) + H₂ (g)

Reaction with dilute acids

• Only metals above hydrogen in the reactivity series will react with dilute acids
• Unreactive metals below hydrogen, such as gold, silver and copper, do not react with acids
• The more reactive the metal then the more vigorous the reaction will be
• Metals that are placed high on the reactivity series such as potassium and sodium are very dangerous and react explosively with acids
• When acids react with metals they form a salt and hydrogen gas:
• The general equation is:

metal + acid ⟶ salt + hydrogen

• Some examples of metal-acid reactions and their equations are given below:

Acid-Metal Reactions Table 

Reaction with oxygen

• Some reactive metals, such as the alkali metals, react easily with oxygen
• Silver, copper and iron can also react with oxygen although much more slowly
• When metals react with oxygen a metal oxide is formed, for example, copper:

metal + oxygen → metal oxide 

2Cu (s) + O₂ (g) → 2CuO (s)

• Gold does not react with oxygen

Deducing the order of reactivity

• The order of reactivity of metals can be deduced by making experimental observations of reactions between metals and water, acids and oxygen
• The more vigorous the reaction of the metal, the higher up the reactivity series the metal is
• A combination of reactions may be needed, for example, the order of reactivity of the more reactive metals can be determined by their reactions with water
• The less reactive metals react slowly or not at all with water, so the order of reactivity would need to be determined by observing their reactions with dilute acid
• Temperature change in a reaction can also be used to determine the order of reactivity
• The greater the temperature change in a reaction involving a metal, the more reactive the metal is