Network solids silicon

Silicon carbide SiC is another network solid. Silicon carbide is used as an abrasive because of its hard structure. 

Even though silicon is metallic in appearance, it is not generally classified as a metal. The electrical conductivity of silicon is so much less than that of ordinary metals it is called a semiconductor. Silicon is an example of a network solid (see Figure 20-1)—it has the same atomic arrangement that occurs in diamond. Each silicon atom is surrounded by, and covalently bonded to, four other silicon atoms. Thus, the silicon crystal can be regarded as one giant molecule. 

In sharp contrast to molecular solids, network solids have very high melting points. Compare the behavior of phosphorus and silicon, third-row neighbors in the periodic table. As listed in Table 11-2. phosphorus melts at 317 K, but silicon melts at 1683 K. Phosphorus is a molecular solid that contains individual P4 molecules, but silicon is a network solid in which covalent bonds among Si atoms connect all the atoms. The vast array of covalent bonds In a network solid makes the entire stmcture behave as one giant molecule. ... 

Much of the Earth s silicon is found in durable rock formations based on silica. Granite is a common example. This is consistent with a network solid. Phosphorus, in contrast. 

Network covalent solids have covalent bonds joining the atoms together in the crystal lattice, which is quite large. Graphite, diamond, and silicon dioxide (Si02) are examples of network solids. 

Silicon carbide, SiC, is a covalent network solid with a structure similar to that of diamond. Sketch a small portion of the SiC structure. 

Silicon nitride (Si3N4), a high-temperature ceramic useful for making engine components, is a covalent network solid in which each Si atom is bonded to four N atoms and each N atom is bonded to three Si atoms. Explain why silicon nitride is more brittle than a metal like copper. 

Diamond, graphite, silicon dioxide, and silicon are examples of substances that form covalent network solids. 

Organic substances such as methane, naphthalene, and sucrose, and inorganic substances such as iodine, sulfur trioxide, carbon dioxide, and ice are molecular solids. Salts such as sodium chloride, potassium nitrate, and magnesium sulfate have ionic bonding structures. All metal elements, such as copper, silver, and iron, have metallic bonds. Examples of covalent network solids are diamond, graphite, and silicon dioxide. 

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. 

Covalently bonded solids such as quartz, diamond, and graphite form another class of crystals. Quartz is a continuous network of silicon dioxide bonded in a uniform, crystalline arrangement. Sand is a mixture of quartz and other rocks. Glass is solid quartz that has melted and resolidified without the same crystalline uniformity, in the way that melted butter does not re-form the same type of solid when it cools. Glass has been known to form naturally in lightning strikes on sand. 

Covalent network solids Atoms such as carbon and silicon, which can form multiple covalent bonds, are able to form covalent network solids. In Chapter 7, you learned how the structures of graphite and diamond give those solid allotropes of carbon different properties. Figure 13-20 shows the covalent network structure of quartz. Based on its structure, will quartz have properties similar to diamond or graphite ... 

Silica is a network solid of silicon and oxygen atoms. The empirical formula for silica is Si02. In silica, to how many oxygen atoms is each silicon bonded ... 

There are some exceptions to this statement, such as network solids, including diamond, silicon, and germanium, where an extended structure is formed even though the bonding is clearly covalent. These examples are discussed in Section 12.7. 

Consider the structures of elements of the third period (Na—Ar). Argon with eight valence electrons has a complete octet as a result it does not form any bonds. Chlorine, sulfur, and phosphorus form molecules (CI2, Sg, and P4) in which the atoms make one, two, and three bonds, respectively ( FIGURE 12.20). Silicon forms an extended network solid in which each atom is bonded to four equidistant neighbors. Each of these elements forms 8—N bonds, where N is the number of valence electrons. This behavior can easily be understood through application of the octet rule. 

Sections 12.7, 12.9) Diamond is a covalent-network solid that has C—C carbon nanotubes have IT bonds that result from the sideways overlap of p orbitals. Elemental silicon, however, exists only as a diamondlike covalent-network solid with cr bonds it has no forms analogous to graphite, buckminsterfullerene, graphene, or carbon nanotubes, apparently because Si— Si tt bonds are weak. 

Silicon is the fundamental component of integrated circuits. Si has the same structure as diamond, (a) Is Si a molecular, metallic, ionic, or covalent-network solid (b) Silicon readily reacts to form silicon dioxide, Si02, which is quite hard and is insoluble in water. Is Si02 most likely a molecular, metallic, ionic, or covalent-network solid ... 

Covalent-network solids consist of atoms held together in large networks or chains by covalent bonds. Because covalent bonds are much stronger than intermolecular forces, these solids are much harder and have higher melting points titan molecular solids. Diamond and graphite, two allotropes of carbon, are covalent-network solids. Other examples include quartz, Si02 silicon carbide, SiC and boron nitride, BN. 

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