Chemical element with the atomic number 6 and unique bonding and crystallisation properties. They result from the 4 valence electrons of the atom. 4 valence electrons allow any kind of bonding and crystallisation and therefore a unique variety of crystallisation forms. Carbon atoms can accept as well as release valence electrons for bonding. They can form double bonds to divalent elements or single bonds to monovalent elements, and also either 4 single bonds or two double bonds or simultaneously one double and two single bonds. Carbon forms the basis for the entire variety of organic polymers. Depending on the conditions of growth, carbon can crystallise to form different substances such as carbon black, diamond, graphene or exotic structures such as fullerene (“football molecule”).