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Rough, uncut diamondsRough, uncut diamondsOne of the most important chemical elements is carbon: it is the fourth most common element in the Universe. Carbon is the main element in all living things. It makes up one-fifth of the human body. Unlike most elements, pure carbon can exist in different forms (allotropes). These include both the soft, black, slippery powder graphite, used as “lead” in pencils, and diamond, the hardest substance of all. Carbon is such a common and adaptable element that it even has its own branch of science, known as organic chemistry.

Graphite, a form of carbon, and a graphite pencilGraphite, a form of carbon, and a graphite pencil
Different carbon-based moleculesDifferent carbon-based molecules

Carbon-based substances

Atoms of carbon can join or bond easily with each other and also with numerous other atoms. This allows carbon to be the basis of a vast variety of substances, from wood to plastics. The structures and substances in all living things—plants and all animals, including humans—are based on carbon. Atoms of carbon easily join with oxygen, nitrogen and hydrogen. In different combinations they form substances such as the sugars and starches found in living things. Even the chemicals which form our genes, known as DNA, have carbon as their main element.

Carbon forms more compounds than any other element: nearly 10 million are known.

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