The number and variety of organic compounds result from the ability of carbon atoms to form covalent bonds with each other as well as with other atoms. Structural formulas show not only the numbers of each kind of atom in a molecule but also how the atoms are joined together. Isomers are compounds with the same molecular formulas but different structural formulas, corresponding to different arrangements of the same atoms. Double bonds and triple bonds are possible between carbon atoms in addition to single ones.
Unsaturated compounds react more readily than saturated ones.
A functional group is a group of atoms whose presence in an organic molecule determines its chemical behavior to a large extent. Plastics, synthetic fibers, and synthetic elastomers are polymers. Carbohydrates are compounds of carbon, hydrogen, and oxygen manufactured in green plants from carbon dioxide and water by photosynthesis with sunlight providing the needed energy. Sugars, starches, and cellulose are carbohydrates. Lipids are fats and fatlike substances such as oils and waxes synthesized from carbohydrates by plants and animals.