• All alkenes contain a?double carbon bond, which is shown as two lines between two of the carbon atoms i.e. C=C
• All alkenes contain a double carbon bond, which is the?functional group?and is what allows alkenes to react in ways that alkanes cannot
• The names and structure of the first four alkenes are shown below:

Table Showing the Formulae and Structures of the First Four Alkenes

• Compounds that have a C=C double bond are also called unsaturated compounds
• That means they can?make more bonds?with other atoms by opening up the C=C bond and allowing incoming atoms to form another single bond with each carbon atom of the functional group
• Each of these carbon atoms now forms 4 single bonds instead of 1 double and 2 single bonds
• This makes them much more reactive than alkanes

A carbon-carbon double can break and form a single bond, allowing more atoms to attach to the carbon atoms