Covalent network solids properties

The nature of the bonds between the structural units of crystalline solids impart other physical properties to these solids. Metals are good conductors of electricity because metallic bonds allow a free flow of electrons. Covalent network, molecular, and ionic solids do not conduct electricity because their bonds do not provide for mobile electrons. Remember, however, that ionic solids in a water solution have free electrons and are good conductors of electricity. Metallic solids are malleable and ductile covalent network solids are brittle and hard. These differences in physical properties are caused by the chemical bonds between the units It is all in the bonds ... 

Crystalline solids can be classified into five categories based on the types of particles they contain atomic solids, molecular solids, covalent network solids, ionic solids, and metallic solids. Table 13-4 summarizes the general characteristics of each category and provides examples. The only atomic solids are noble gases. Their properties reflect the weak dispersion forces between the atoms. 

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 ... 

There are some solids, often called covalent network solids, that are composed only of atoms interconnected by a network of covalent bonds. Quartz and diamond are two common examples of network solids. In contrast to molecular solids, network solids are typically brittle, nonconductors of heat or electricity, and extremely hard. Analyzing the structure of a diamond explains some of its properties. In a diamond, each carbon atom is bonded to four other carbon atoms. This tetrahedral arrangement, which is shown in Figure 8.25, forms a strongly bonded crystal system that is extremely hard and has a very high melting point. 

What is the difference between a covalent molecular solid and a covalent network solid Do their physical properties differ Explain your answer. 

Skill 22.6 Classify unknown solids as molecular, metallic, ionic, and covalent network solids according to their physical and chemical properties. 

Most metals are malleable, which means that they can be hammered into thin sheets, and ductile, which means that they can be drawn into wires ( FIGURE 12.10). These properties indicate that the atoms are capable of slipping past one another. Ionic and covalent-network solids do not exhibit such behavior. They are typically brittle and fracture easily. Consider, for example, the difference between dropping a ceramic plate and an aluminum cooking pan onto a concrete floor. 

Both covalent-network solids and ionic solids can have melting points well in excess of room temperature, and both can be poor conductors of electricity in their pure form. However, in other ways their properties are quite different. 

Which of the following properties are typical characteristics of a covalent-network solid, a metallic solid, or both (a) ductility, (b) hardness, (c) high melting point ... 

Solids can be classified in terms of the type of force between the structural units there are molecular, metallic, ionic, and covalent network solids. Melting point, hardness, and electrical conductivity are properties that can be related to the structure of the solid. 

Questions 59 and 60 The physical properties of four solids are tabulated below. In each case, state whether the solid is most likely to be ionic, molecular, metallic, or a covalent network solid. 

A few solids make an almost infinite three-dimensional array of covalent bonds to neighboring atoms. Such solids are called covalent network solids. Diamond (a form of carbon), elemental silicon, elemental germanium, and silicon dioxide are examples (see Figure 21.3). Although few solids can be described this way, the ones that can have distinctive properties They are very hard with high melting points. It takes a lot of energy, either mechanical or thermal, to break the almost infinite network of covalent bonds. 

Solids can be classified into four categories ionic, metallic, covalent network, and molecular. For each of the four categories, identify the basic structural unit describe the nature of the force both within the unit and between units cite the basic properties of each type of solid give two examples of each type of solid and describe a laboratory means of identifying each type of solid. 

Trends in properties, such as decreasing hardness and melting point, are due to changes in types of bonding within the solid covalent network in C, Si, and Ge metallic in Sn and Pb [see text). Down the group, density increases because of several factors, including differences in crystal packing. 

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