What is here?
Use your mouse (or finger on touch devices) to move or scale molecules. Double tap to stop and start each animation.
A homologous series is a series of compounds which:
- have the same functional group
- have the same general formula
- differ by CH2 in molecular formulae from neighbouring compounds
- show a gradual variation in physical properties, such as their boiling points
- have similar chemical properties.
A functional group is an atom, group of atoms or a bond responsible for the characteristic chemical reactions of a substance. The functional group in alkanes is most easily shown as —CH3.
A general formula is a chemical formula used to represent the members of a homologous series. The general formula for the alkanes is CnH2n+2.
Hexane molecules, for example, contain six carbon atoms:
n = 6
2n + 2 = (2 × 6) + 2 = 14
So the molecular formula for hexane is C6H14.
Structural and displayed formulae
A structural formula shows the number of atoms of each element in a molecule, and their positions in the molecule.
A displayed formula shows the same information as a structural formula, but in addition it shows the bonds between the atoms.
|Name of alkane||Structural formula||Displayed formula|