Malleable metallic solids

However, ultrasonic rate enhancements of heterogeneous catalysis have usually been relatively modest (less than tenfold). The effect of irradiating operating catalysts is often simply due to improved mass transport (58). In addition, increased dispersion during the formation of catalysts under ultrasound (59) will enhance reactivity, as will the fracture of friable solids (e.g., noble metals on C or silica (60),(62),(62) or malleable metals (63)). 

Platinum (Pt, [Xe + 4/ l4]5r/96.s 1), name from the Spanishplatina (silver). Known and used by the pre-Columbian South-American Indians since ancient times. Re-discovered and noticed by the Western scientists in 1735 (Antonio de Ulloa). Silvery, white solid, ductile and malleable metal. 

Metallic solids are excellent electrical and thermal conductors. They are ductile and malleable. When a piece of metal is forced to take a different shape, it continues to hold together since its electrons can shift to bond the metallic atoms in their new positions. 

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 ... 

Metallic solids contain atoms bonded together by metallic bonds. These bonds are strong but not localized. Since the electrons in the metallic bonds are relatively mobile, metals tend to have high melting points and be hard, malleable, nonvolatile and shiny. Metals are soluble neither in water nor organic solvents. Some metals, such as sodium, dissolve by reacting with water. Metals sometimes dissolve in liquid metallic mercury. 

Malleability and ductility These terms refer respectively to how readily a solid can be shaped by pressure (forging, hammering, rolling into a sheet) and by being drawn out into a wire. Metallic solids are known and valued for these qualities, which derive from the non-directional nature of the attractions between the kernel atoms and the electron fluid. The bonding within ionic or covalent solids may be stronger, but it is also directional, making these solids subject to fracture (brittle) when struck with a hammer, for example. A metal, by contrast, is more likely to be simply deformed or dented. 

The electron sea model can explain the melting point, boiling point, malleability, conductivity, and ductihty of metallic solids. 

Metallic solids Recall from Chapter 8 that metallic solids consist of positive metal ions surrounded by a sea of mobile electrons. The strength of the metallic bonds between cations and electrons varies among metals and accounts for their wide range of physical properties. For example, tin melts at 232°C, but nickel melts at 1455°C. The mobile electrons make metals malleable—easily hammered into shapes—and ductile—easily drawn into wires. When force is applied to a metal, the electrons shift and thereby keep the metal ions bonded in their new positions. Read Everyday Chemistry at the end of the chapter to learn about shape-memory metals. Mobile electrons make metals good conductors of heat and electricity. Power lines carry electricity from power plants to homes and businesses and to the electric train shown in Figure 13-21a. 

In general, metallic solids are ductile and malleable, whereas ionic salts are brittle and shatter readily (although they are hard). Explain this observation. 

PHYSICAL PROPERTIES reddish solid lustrous, ductile, and malleable metal face-centered cubic (fee) structure becomes dull upon exposure to air becomes coated with a green layer of basic carbonate in moist air odorless solid slowly soluble in ammonia water soluble in nitric acid, hot concentrated sulfuric acid, and hydrogen bromide very slightly soluble in hydrochloric acid and ammonium hydroxide insoluble in hot and cold water copper fume is characterized by finely divided black particulates dispersed in air MP (1083°C, 1981°F) BP (2595°C, 4703°F) DN (8.94 g/cm ) SG (8.94) CP (0.092 cal/g/° C solid at 20° C, 0.112 cal/g/°C liquid at 20°C) HV (1150 cal/g) VD (NA) VP (0 mmHg approximately) MOHS HARDNESS (3.0). 

PHYSICAL PROPERTIES bluish-black, amorphous powder or grayish-white lustrous metal soft, malleable, ductile solid hexagonal lattice below 865°C, body-centered cubic above 865°C may become embrittled by the absorption of nitrogen, oxygen, and carbon soluble in hot, very concentrated acids insoluble in water and cold acids MP (1857°C, 3375°F) BP (3577°C, 6471°F) DN (6.506 g/cm at 20°C) SG (6.51) CP (25.4 J/K-mol crystal at 25°C) VD (NA) VP (0 mmHg at 20 C) BHN (85). 

Physical Description Metal Soft, malleable, ductile, solid or gray to gold, amorphous poyirder. 

SECTION 12.3 Metallic solids are typically good conductors of electricity and heat, malleable, which means that they can be hammered into thin sheets, and ductile, which means that they can be drawn into wires. Metals tend to form structures where the atoms are closely packed. Two related forms of close packing, cubic ciose packing and hexagonal close packing, are possible. In both, each atom has a coordination number of 12. 

Another type of defect, known as an edge dislocation, occurs most often in metallic solids where an extra half plane of atoms inserts itself into the lattice, as shown in Figure 12.29. The point of termination of this half plane is known as the dislocation. The presence of a dislocation in a metallic solid makes it more susceptible to deformation. Metals having a large number of edge dislocations, such as lead or white tin, are very malleable. In other substances, such as copper or iron, it is even possible to hammer out the dislocation by mechanical force. 

Metallic Solids Most metallic elements crystallize in one of the two closest packed structures (Figure 12.30). In contrast to the weak dispersion forces in atomic solids, powerM metallic bonding forces hold atoms together in metallic solids. The properties of metals— high electrical and thermal conductivity, luster, and malleability— result from their delocalized electrons (Section 9.1). Melting points and hardnesses of metallic solids are also related to packing efficiency and number of valence electrons. We discuss bonding models that explain these metallic properties in the next two subsections. 

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