Electrical and thermal conductivity: Carbon has four valence electrons.This makes graphite soft and hence a useful dry (solid) lubricant for heavy machinery. Therefore, one layer can easily slide over the other. Softness: The various layers of carbon atoms in graphite are held together by weak van der Waals forces of attraction.Low density: Due to wide spacing (340 pm) between the two layers, the carbon atoms in graphite are less closely packed and hence the density of graphite (2.22 g cm –3) is much lower than that of diamond.When we write with a pencil, layers of graphite flake off and stick to the paper. The layers are able to slide easily over one another, rather like pack of cards. However, the bonds between the layers are weak. So graphite also has a high melting point. The carbon atoms are difficult to separate from one another. This forms a pattern of interlocking hexagonal rings. Within each layer of graphite, every carbon atom is joined to three others by strong covalent bonds. This makes graphite lubricating, soft and greasy to touch. The layers can therefore, easily slide over one another. The different layers are held together by weak forces, called vanderwaal forces. It is also prepared artificially from carbon in an electric furnace at 2273–2773 K.Įach carbon is bonded to only three neighboring carbon atoms in the same plane forming layers of hexagonal networks separated by comparatively larger distance. It occurs in nature mixed with mica, quartz and silica. Occurrence: Graphite is a grayish black substance.
0 kommentar(er)
