Carbon and Silicon Network Atomic Solids

The Composition of the Two Brands of Steel Tubing Most Commonly Used to Make Lightweight Racing Bicycles 

7% copper, 6% bismuth, and 2% antimony), and plumber s solder (67% lead and 33% tin) are other examples of substitutional alloys. 

Many types of steel contain elements in addition to iron and carbon. Such steels are often called alloy steels and can be viewed as being mixed interstitial (carbon) and substitutional (other metals) alloys. Bicycle frames, for example, are constructed from a wide variety of alloy steels. The compositions of the two brands of steel tubing used in high-quality racing bicycles are given in Table 16.3. 

Many atomic solids contain strong directional covalent bonds. We will call these substances network solids. In contrast to metals, these materials are typically brittle and do not efficiently conduct heat or electricity. To illustrate network solids, in this section we will discuss two very important elements, carbon and silicon, and some of their compounds. 

Carbon occurs in the allotropes (different forms) diamond, graphite, and the fullerenes. The fullerenes are molecular solids (see Section 16.6), but diamond and graphite are typically network solids. In diamond, the hardest naturally occurring substance, each carbon atom is surrounded by a tetrahedral arrangement of other carbon atoms, as shown in Fig. 16.26(a). This structure is stabilized by covalent bonds, which, in terms of the localized electron model, are formed by the overlap of sp hybridized atomic orbitals on each carbon atom. 

The structures of (a) diamond and (b) graphite. In each case only a small part of the entire structure is shown. 

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Since the isolation of sheets of graphene by Gein and Novoselov, research in the properties and possible uses of this material has virtually exploded. Graphene has truly amazing properties. For example, it is believed 

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