Glossary

Carbon is a nonmetallic chemical element with the symbol C and atomic number 6. It is one of the most fundamental elements in the universe—forming the backbone of all known life and serving as a key building block in materials, fuels, and industrial compounds.

In its pure form, carbon exists in several allotropes, meaning it can take different structural forms with distinct physical properties. The three best-known are:

- Diamond – each carbon atom is bonded to four others in a tetrahedral lattice, making it the hardest natural material known. Diamonds are transparent, excellent electrical insulators, and extremely thermally conductive.

- Graphite – carbon atoms are arranged in flat hexagonal layers, with weak forces between the sheets. This gives graphite its slippery texture (used in lubricants and pencils) and makes it an excellent electrical conductor.

- Amorphous carbon – includes coal, charcoal, soot, and carbon black, where atoms lack long-range order but still form strong covalent networks.

Modern discoveries have revealed additional allotropes, such as graphene (a single layer of graphite atoms with extraordinary electrical and mechanical strength), fullerenes (C₆₀ “buckyballs”), and carbon nanotubes, all of which have revolutionized nanotechnology and materials science.

Carbon’s atomic structure—four valence electrons—allows it to form strong covalent bonds with many elements, including itself. This bonding flexibility enables carbon to create millions of compounds, more than any other element. These include organic molecules such as hydrocarbons, proteins, DNA, and polymers, making carbon the basis of organic chemistry and, by extension, life itself.

In industry, carbon is used in countless ways. It appears in steelmaking (as a strengthening alloying element), graphite electrodes, activated carbon filters, composite materials, carbon fiber, inks, and electrodes for batteries and fuel cells. Carbon compounds also form the foundation of the petrochemical industry—fuels like methane, gasoline, and propane are all carbon-based hydrocarbons.

Carbon is an essential part of Earth’s biosphere and atmosphere. It circulates through the carbon cycle, moving between the air (as carbon dioxide, CO₂), oceans, plants, animals, and fossil fuels. This cycle regulates global climate and supports life through photosynthesis and respiration.