GCSE SCIENCE CHEMISTRY HIGH SCHOOL - Structure - Alkanes - Homologous Series - Formula - General

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Structure of Alkane Hydrocarbons.

Alkanes form an homologous series, with the general formula C_nH_2n+2.
Homologous means that they have similar properties and structure,
differing only in the number of CH₂ units in the chain.
The "chain" is the line of carbon atoms joined together.
Members of the same series show a gradual change in physical properties
for example the boiling point increases as the chain gets longer.

Methane, CH₄, has n=1.	Pentane, C₅H₁₂, has n=5.
Ethane, C₂H₆, has n=2.	Hexane, C₆H₁₄, has n=6.
Propane, C₃H₈, has n=3.	Heptane, C₇H₁₆, has n=7.
Butane, C₄H₁₀, has n=4.	Octane, C₈H₁₈, has n=8.

Below are links to the structure of alkanes. Some of these exist as isomers.
The structural formula is sometimes called the displayed formula.

Methane	Pentane
Ethane	Hexane
Propane	Heptane
Butane	Octane

Alkanes are hydrocarbons which have single bonds between all the atoms.
They have the maximum number of hydrogen atoms
for the number of carbon atoms present,
and so alkanes are called saturated hydrocarbons.

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