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Combined Science
Key terms
Ionic equation

GCSE Combined Science · key term

Ionic equation

Definition

An equation showing only the particles involved in the chemical change, with unchanged spectator ions omitted.

Used by AQA and Edexcel

How each exam board covers it

AQA GCSE Combined Science Trilogy · 8464

Specification 5.1.1.1, 5.4.1.4, 5.4.2.4 · Paper 3

An ionic equation focuses on the particles that actually change. Consider the neutralisation of hydrochloric acid by sodium hydroxide.
Revise: Representing Chemical Reactions and Balancing Equations
An equation showing the reacting ions and other reacting substances, with unchanged spectator ions omitted.
Revise: Oxidation and Reduction via Electrons
An equation showing the ions that take part in a reaction, rather than ions that remain unchanged.
Revise: The pH Scale and Neutralisation

AQA Combined Science Trilogy past papers

Edexcel GCSE Combined Science · 1SC0

Specification Formulae, equations and hazards · Paper 3, Paper 4

An equation showing only the species that change during a reaction, with both atoms and total electrical charge balanced.
An ionic equation focuses on the species that actually change. Dissolved ionic compounds contain separate ions, and some of those ions may remain unchanged throughout a reaction.
Revise: Chemical formulae and equations

Edexcel Combined Science past papers

Exam tips

1
Cancel only spectator ions that appear unchanged on both sides of an ionic equation.
2
In ionic equations, cancel only species that are identical on both sides. Check both atom numbers and total charge.

Related key terms

Spectator ion
Coefficient
Half-equation
Oxidation
Product
Reactant
Reduction
State symbol
Subscript
Acid

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