Carbon forms four bonds in its compounds
ethene
ethyne
The structures at the right show that singly bonded carbons
at the end of the chain are also bonded to three hydrogens
bonded to two other atoms are also bonded to two hydrogens.
bonded to three other atoms are also bonded to one hydrogen.
bonded to two other atoms are also bonded to two hydrogens.
bonded to three other atoms are also bonded to one hydrogen.
Note that the number of hydrogens and carbons in the branched and straight chain compounds at the right are the same, but the atom-to-atom bonding sequence is different. Such compounds are known as constitutional isomers.
Carbon atoms may also be joined by multiple bonds.
In ethene the carbon atoms share four electrons (double bond).
This is represented by two lines between the bonded atoms.
In ethyne the carbon atoms share six electrons (triple bond).
This is represented three lines between the bonded atoms.
This is represented by two lines between the bonded atoms.
In ethyne the carbon atoms share six electrons (triple bond).
This is represented three lines between the bonded atoms.
Compounds that have only single bonds are referred to as saturated because there is the maximum number of hydrogens are attached to each atom. Ethene and ethyne are referred to as unsaturated because they have fewer hydrogens than the maximum at their carbons due to the multiple bond.