Alkanes
The alkanes are a homologous seriesA 'family' of organic compounds that have the same functional group and similar chemical properties. of hydrocarbonA compound that contains hydrogen and carbon only.. This means that they have similar chemical properties to each other and they have trends in physical properties. For example, as the chain length increases, their boiling point increases.
The alkanes share the same general formula.
CnH2n+2
The general formula means that the number of hydrogen atomAll elements are made of atoms. An atom consists of a nucleus containing protons and neutrons, surrounded by electrons. in an alkane is double the number of carbon atoms, plus two. For example, methane is CH4 and ethane is C2H6.
Alkane moleculeA collection of two or more atoms held together by chemical bonds. can be represented by displayed formulae in which each atom is shown as its symbol (C or H) and the covalent bondA bond between atoms formed when atoms share electrons to achieve a full outer shell of electrons. between them by a straight line.
Here are the names and structures of five alkanes:
Alkanes are saturated hydrocarbons. This means that their carbon atoms are joined to each other by single bonds. This makes them relatively unreactive, apart from their reaction with oxygen in the air 鈥 which we call burning or combustion.
[Higher tier only]
Like other homologous series, the alkanes show isomerism. This means that their atoms can be arranged differently to make slightly different compoundA substance formed by the chemical union of two or more elements. with different properties. For example, an isomerChemicals that have the same molecular formula but different arrangements of atoms. of butane is methylpropane.