Reactivity Series (CIE IGCSE Chemistry: Co-ordinated Sciences (Double Award))

What is the reactivity series of metals?

• 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

Reactivity Series of Metals

Metal	Reaction with cold water	Reaction with acid	Reaction with oxygen
Most reactive
Potassium	Reacts violently	Reacts violently	Reacts quickly in air
Sodium	Reacts quickly	Reacts quickly	Reacts quickly in air
Calcium	Reacts less strongly	Reacts vigorously	Reacts readily
Magnesium	Slow reaction (reacts with steam)	Reacts vigorously	Reacts readily
Aluminium	Slow reaction (reacts with steam)	Reacts readily	Reacts readily
Carbon
Zinc	Very slow reaction (reacts slowly with steam)	Reacts less strongly	Reacts
Iron	Very slow reaction (reacts slowly with steam)	Reacts less strongly	Reacts
Hydrogen
Copper	No reaction with steam or water	No reaction	Reacts
Silver	No reaction with steam or water	No reaction	Reacts
Gold	No reaction with steam or water	No reaction	No reaction
Least reactive

How to remember the reactivity series

• 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"

Reactivity Series Mnemonic

Metal	Abbreviation
Most reactive
Potassium	P - Please
Sodium	S - send
Calcium	C - cats,
Magnesium	M - monkeys,
Aluminium	A - and
Carbon	C - cute
Zinc	Z - zebras
Iron	I - into
Hydrogen	H - hot
Copper	C - countries
Silver	S - signed
Gold	G - Gordan
Least reactive

Reaction of metals 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)

2K (s) + 2H₂O (l) → 2KOH (aq) + H₂ (g)

Reactions of metals 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 

Acid	Sulfuric acid	Hydrochloric acid
Magnesium	Mg + H2SO4 → MgSO4 + H2	Mg + 2HCl → MgCl2 + H2
Zinc	Zn + H2SO4 → ZnSO4 + H2	Zn + 2HCl → ZnCl2 + H2
Iron	Fe + H2SO4 → FeSO4 + H2	Zn + 2HCl → ZnCl2 + H2

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