IGCSEChemistryEdexcelChemistry (Modular)Unit 1Revision Notes4. Organic Chemistry: Part 1AlkanesWhat are Alkanes?

What are Alkanes? (Edexcel IGCSE Chemistry (Modular): Unit 1): Revision Note

Exam code: 4XCH1

Written by: Stewart Hird

Reviewed by: Lucy Kirkham

Updated on 22 October 2026

Alkanes

What are alkanes?

Alkanes are a group of saturated hydrocarbons
The term saturated means that they only have single carbon-carbon bonds, there are no double bonds
The general formula of the alkanes is C_nH_2n+2
Alkanes are generally unreactive compounds but they do undergo combustion reactions, can be cracked into smaller molecules and can react with halogens in the presence of light
Methane is an alkane and is the major component of natural gas

The first five alkanes

The first five members of the alkanes are:
Methane
- Molecular formula: CH₄

Displayed formula of methane: one carbon atom single-bonded to four hydrogen atoms, arranged above, below, left and right.

Ethane
- Molecular formula: C₂H₆

Displayed formula of ethane: two carbon atoms joined by a single bond, with three hydrogen atoms attached to each carbon.

Propane
- Molecular formula: C₃H₈

Displayed formula of propane: three carbon atoms in a straight chain joined by single bonds, with three hydrogen atoms on each end carbon and two on the central carbon.

Butane
- Molecular formula: C₄H₁₀

Displayed formula of butane: four carbon atoms in a straight chain joined by single bonds, with three hydrogen atoms on each end carbon and two on each internal carbon.

Pentane
- Molecular formula: C₅H₁₂

Displayed formula of pentane: five carbon atoms in a straight chain joined by single bonds, with three hydrogen atoms on each end carbon and two on each internal carbon.

Examiner Tips and Tricks

For your exam, you need to be able to name, draw and give the appropriate formula for the first five alkanes.

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