Carbon can exist in several forms, including graphite, one of the softest naturally occurring substances, and diamond, one of the hardest naturally occurring substances. Carbon has the highest melting point of all the elements and, in the diamond form, has the highest thermal conductivity of any element.
Carbon is the fourth most abundant chemical element in the universe by mass after hydrogen, helium and oxygen. Carbon is abundant in the Sun, stars, comets and in the atmospheres of most planets.
Carbon, as a coal, is used as a fuel. As graphite, it is used as a lubricant, for pencil tips, high temperature crucibles, dry cells and electrodes. As a diamond, it is used in jewelry and it is in industry for cutting, drilling, grinding, and polishing. Carbon black is used as the black pigment in printing ink. Carbon is also used in archaeological chemical dating and to form alloys with iron, creating carbon steel.
Carbon has an affinity for bonding with other small atoms, including other carbon atoms, and is capable of forming multiple stable covalent bonds with them. Carbon forms a number of compounds with hydrogen, oxygen, nitrogen and other elements. Its ability to form long-chained, complex compounds makes carbon the basis of all life on Earth.