Carbon atoms have a strong ability to form "chemical hand-in-hand" bonds, and can form many different structures through three types of chemical bonds, namely single bonds, double bonds, and triple bonds. Carbon atoms alone can form completely different structures and properties of diamond, graphite, graphene, carbon 60, carbon nanotubes, and other carbon elements. These different forms of the same element are called allotropes.
In the crystal of diamond, each carbon atom is surrounded by four adjacent carbon atoms and bonded to these four carbon atoms by covalent bonds to form a tetrahedral structure. The crystal of graphite is a layered structure. In each layer, each carbon atom is bonded to three other carbon atoms by covalent bonds, arranged into a flat hexagonal layered structure. Graphene is a single layer of graphite, which can now be artificially produced and has extremely wide applications.
Any single carbon element can be transformed under conditions created by humans, just like Sun Wukong's "72 transformations". By heating and high-temperature recrystallization, charcoal can be transformed into graphite; graphite can be transformed into diamond under high temperature and high pressure; under the action of arc discharge, graphite can form single or numerous carbon atoms. If these atoms are allowed to regrow, they can form allotropes of carbon such as graphene, carbon 60, and carbon nanotubes under different conditions.
Carbon 60 is a closed cage-like molecule formed by 60 carbon atoms, just like a football. Scientists have also discovered many single-element substances composed of carbon, existing in spherical, oval, or tubular structures. These substances have bizarre structures, like some ingeniously designed buildings, and are therefore named after architect Fuller and called fullerenes. Among them, columnar or tubular molecules are called carbon nanotubes or buckytubes.