Changes

Alkenes are organic molecules which contain at least one C=C bouble bond.  An alkene has the suffix -ene.  Ethene is the simplest alkene possible with 2 carbon atoms double bonded to each other and 4 hydrogen atoms.  Methene (1 carbon atom) is an impossible chemical because there is nowhere to put a double bond between carbon atoms

Alkenes are organic molecules which contain at least one C=C bouble bond.  An alkene has the suffix -ene.  Ethene is the simplest alkene possible with 2 carbon atoms double bonded to each other and 4 hydrogen atoms.  Methene (1 carbon atom) is an impossible chemical because there is nowhere to put a double bond between carbon atoms

Alkenes longer than ethene have an added complication.  It is essential to state the relative position of a double bond.  Butene for example can have the double bond in two different positions (Hydrogen atoms ommitted):  C=C-C-C or C-C=C-C. The first is still called Butene, the second is But-2-ene.  The 2 comes from the double bond being attached to the second carbon in the chain.

Alkenes longer than ethene have an added complication.  It is essential to state the relative position of a double bond.  Butene for example can have the double bond in two different positions (Hydrogen atoms ommitted):  C=C-C-C or C-C=C-C (C-C-C=C is identical to C=C-C-C). The first is still called Butene, the second is But-2-ene.  The 2 comes from the double bond being attached to the second carbon in the chain.

Using butene as an example again it can be seen that there is enough space for more than one double bond: C=C=C-C, C=C-C=C or even C=C=C=C.  These are respectively called But-1,2-diene, But-1,3-diene and but-triene.  Again the numbers 1,2 and 3 signify the position the carbon bond.  but-triene does not need any positioning numbers because there is no other way of arranging the double bonds.  The 'di' and 'tri' signify that there is more than one double bond in the chain.

Using butene as an example again it can be seen that there is enough space for more than one double bond: C=C=C-C, C=C-C=C or even C=C=C=C.  These are respectively called But-1,2-diene, But-1,3-diene and but-triene.  Again the numbers 1,2 and 3 signify the position the carbon bond.  but-triene does not need any positioning numbers because there is no other way of arranging the double bonds.  The 'di' and 'tri' signify that there is more than one double bond in the chain.