Carbon

Carbon is a chemical element with atomic number Z = 6, i.e., the carbon nucleus has charge 6e, where e is the elementary charge, and carbon takes the sixth position in the periodic table of elements. The chemical symbol of carbon is C. One twelfth of the mass (formerly called atomic weight) of the most abundant isotope ¹²C is by definition the unified atomic mass unit: A(¹²C) ≡ 1 u. The atomic mass averaged over the naturally occurring isotopes is 12.0107 u.

One of the most widely distributed and abundant of all elements, carbon is a constituent of all organic matter. Diamond, graphite, and fullerenes are non-organic compounds consisting of carbon only; these are known as allotropes of carbon. Most organic carbon compounds contain hydrogen; those that contain oxygen as well include the extensive class of carbohydrates.

Plastics, drugs, animal and plant tissue, foods, textile, wood, paper, and many other common substances contain carbon. Fossil fuels (coal, petroleum, natural gas, etc.) are compounds of carbon. The greenhouse gas carbon dioxide CO₂ is an oxide of carbon, as is the poisonous gas carbon monoxide (CO).