The Chemistry of Life | Biology

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The Chemistry of Life

Carbon Chemistry

Carbon is a chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. Carbon is the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. Carbon is abundant in the solar system, chiefly as carbon dioxide (CO2) or methane (CH4). The very next element is oxygen, making carbon and oxygen the most abundant elements in the universe. The atoms of carbon can bond together in different ways, termed allotropes of carbon. The best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form. For example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper (hence its name, from the Greek "to write"), while diamond is the hardest naturally occurring material known. Graphite is a very good conductor of heat, while diamond has a low thermal conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivity of all known materials. All carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form at standard temperature and pressure. They are chemically resistant and require high temperature to react even with oxygen.

Dennis Howard

Elements and Their Atoms

The Elements of Life

Chemical Bonds and Reaction Basics

Life in Aqueous Solution

Carbon Chemistry

Monomers and Polymers

Carbohydrates

Proteins

Nucleic Acids

Lipids