Elemental Forms of Carbon

We have seen that carbon exists in several allotropic crystalline forms graphite, diamond, fullerenes, carbon nanotubes, and graphene. Fullerenes, nanotubes, and graphene are discussed in Chapter 12 here we focus on graphite and diamond. 

Graphite is a soft, black, slippery solid that has a metallic luster and conducts electricity. It consists of parallel sheets of sp -hybridized carbon atoms held together by 

Graphite has a well-defined crystalline structure, but it also exists in two common amorphous forms carbon black and charcoal. Carbon black is formed when hydrocarbons are heated in a very limited supply of oxygen, such as in this methane reaction  

Carbon black is used as a pigment in black inks large amounts are also used in making automobile tires. 

Charcoal is formed when wood is heated strongly in the absence of air. Charcoal has an open structure, giving it an enormous surface area per unit mass. Activated charcoal, a pulverized form of charcoal whose surface is cleaned by heating with steam, is widely used to adsorb molecules. It is used in filters to remove offensive odors from air and colored or bad-tasting impurities from water. 

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Pencil lead" is almost pure graphite. Graphite is the stable elemental form of carbon at 25°C and 1 atm. Diamond is an allotrope of graphite. Given... 

Many compounds of carbon, particularly the hydrocarbons, are not only toxic but also carcinogenic (cancer-causing), but the elemental forms of carbon, such as diamonds and graphite, are not considered toxic. 

Diamond, graphite, and fullerene are elemental forms of carbon which have very different properties but which are all solids at room temperature. Looking at the 3D models of diamond, graphite, and fullerene in eChapter 19.6, what intermolecular forces do you expect to find in each ... 

Until 1985, the only known elemental forms of carbon were diamond, graphite, and amorphous carbon. Then Kroto et al. announced the discovery of C6o, a spherical arrangement of carbon atoms in hexagons and pentagons, as shown in Figure 17.7. They called this form Buckminsterfullerene after the architect Buckminster Fuller, who developed the geodesic dome. The name for this type of carbon molecule has since been shortened to fullerene, but it is commonly called a buckyball. Since this first discovery, it has been found that fullerenes can be made in quantity from electrical arcs between graphite electrodes. About 75% of... 

Other elemental forms of carbon in primitive meteorites... 

The two most common elemental forms of carbon are diamond and graphite. Diamond, one of the hardest substances known, is used for industrial cutting tools, whereas graphite, a slippery black substance, is used as a lubricant. Their physical characteristics are so different because their molecular structures are very different. 

Buckminsterfullerene (Ceo) is a third elemental form of carbon. Its structure consists of 20 hexagons and 12 pentagons of sp hybridized carbon atoms joined in a spherical arrangement. It is completely conjugated because each carbon atom has a p orbital with an electron in it. 

The three solid elemental forms of carbon (allotropes) diamond, graphite, and buckminsterfullerene. The representations of diamond and graphite are fragments of much larger structures that extend in all directions from the parts shown here. Buckminsterfullerene contains Cgo molecules, one of which is shown. 

The ready ability of period 2 elements to form it bonds is an important factor in determining the structures of these elements and their compounds. Compare, for example, the elemental forms of carbon and silicon. Carbon has five major crystalline allotropes diamond, graphite, buckminsterfullerene, graphene, and carbon nanotubes. 

Another very common layered structure is given by graphite, 13.58, one of the elemental forms of carbon. The other common structure is diamond, 13.59. 

The three solid elemental forms of carbon (allotropes) (a) diamond,... 

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