Unique properties of carbon
Carbon has a number of unique properties which influence how it behaves and how it bonds with other atoms:
Carbon has four valence electrons which means that each carbon atom can form four bonds with other atoms. Because of this, long chain structures can form. These chains can either be unbranched (Figure 1) or branched (Figure 2). Because of the number of bonds that carbon can form with other atoms, organic compounds can be very complex.
Figure 1: An unbranched carbon chain Figure 2: A branched carbon chain
Because of its position on the Periodic Table, most of the bonds that carbon forms with other atoms are covalent. Think for example of a bond. The difference in electronegativity between the two atoms is zero, so this is a pure covalent bond. In the case of a bond, the difference in electronegativity between carbon (2,5) and hydrogen (2,1) is so small that bonds are almost purely covalent. The result of this is that most organic compounds are non-polar. This affects some of the properties of organic compounds.