IGCSE Chemistry
2026 - 2028
Syllabus Checklist ✅
Topic 8: Redox
Oxidation Numbers
Use a Roman numeral
to indicate the oxidation number
of an element in a compound
Definitions of Redox
Define redox reactions
as involving simultaneous oxidation
and reduction
Define oxidation
as gain of oxygen
and reduction
as loss of oxygen
Identify redox reactions
as reactions involving gain
and loss of oxygen
Identify oxidation
and reduction
in redox reactions
Electron and Oxidation-Number Definitions
Define oxidation
in terms of:
(a) loss of electrons
(b) an increase in oxidation number
Define reduction
in terms of:
(a) gain of electrons
(b) a decrease in oxidation number
Identify redox reactions
as reactions involving gain
and loss of electrons
Rules for Oxidation Numbers
Identify redox reactions
by changes in oxidation number
using:
(a) the oxidation number of elements in their uncombined state
is zero
(b) the oxidation number of a monatomic ion
is the same as its charge
(c) the sum of oxidation numbers in a compound
is zero
(d) the sum of oxidation numbers in an ion
equals the charge on the ion
Experimental Identification
Identify redox reactions
by the colour changes
involved when using acidified aqueous potassium manganate(VII)
or aqueous potassium iodide
Oxidising and Reducing Agents
Define an oxidising agent
as a substance that oxidises another substance
and is itself reduced
Define a reducing agent
as a substance that reduces another substance
and is itself oxidised
Identify oxidising agents
and reducing agents
in redox reactions
