KENNETH EWARD / BIOGRAFX / SCIENCE PHOTO LIBRARY KENNETH EWARD / BIOGRAFX / SCIENCE PHOTO LIBRARY
Graphite. Molecular graphic of graphite, one of the naturally existing allotropes of the element carbon. Carbon atoms are represented by blue spheres. Graphite is used in pencil leads and as a lubricant. It has a crystalline structure composed of parallel layers of hexagonally arranged carbon atoms. Within each layer, carbon atoms are linked by strong aromatic bonds, while the parallel layers are held together by weak intermolecular forces called Van der Waals' forces. This Van der Waals's bonding is strong enough to hold the layers together, yet weak enough to allow them to slide over each other. This also confers graphite's softness and its ability to act as a lubricant.
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