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Key Concepts PowerPoint

Chapter 21
Metals and Solid-State Materials

  
21-02
Title
 Mineral Sources of Metals
Caption
 Figure 21.2 Primary mineral sources of metals. The s-block metals occur as chlorides, silicates, and carbonates. The d-and p-block metals are found as oxides and sulfides, except for the group 3B metals, which occur as phosphates, and the platinum-group metals and gold, which occur in uncombined form. There is no mineral source of technetium (Tc in group 7B), a radioactive element that is made in nuclear reactors.
Notes
 Periodic table showing the primary mineral sources of metals.
Keywords
 mineral source, metals
21-03
Title
 Concentration of Metal Sulfide Ores
Caption
 Figure 21.3 The flotation process for concentrating metal sulfide ores. Mineral particles float to the top of the tank along with the soapy air bubbles, while the gangue sinks to the bottom.
Notes
 Diagram of the flotation process for concentrating metal sulfide ores.
Keywords
 metallurgy, flotation process, metal sulfide
21-03-01UN
Title
 Reduction Methods
Caption
 Table 21.2 Reduction methods for producing some common metals.
Notes
 In general, the ease of reducing an ore to the free metal increases from left to right of the periodic table.
Keywords
 reduction
21-05
Title
 Reduction of Iron Ore
Caption
 Figure 21.5 A diagram of a blast furnace for reduction of iron ore. Modern blast furnaces are as large as 60 m in height and 14 m in diameter. They are designed for continuous operation and produce up to 10,000 tons of iron per day. Note the approximate temperatures and the chemical reactions that occur in the various regions of the furnace.
Notes
 Diagram of a blast furnace for reduction of iron ore.
Keywords
 iron, reduction, blast furnace
21-06
Title
 Electron-Sea Model
Caption
 Figure 21.6 Two-dimensional representation of the electron-sea model of a metal. An ordered array of cations is immersed in a continuous distribution of delocalized, mobile valence electrons. The valence electrons do not belong to any particular metal ion but to the crystal as a whole.
Notes
 The electron-sea model of a metal.
Keywords
 electron-sea model
21-07
Title
 Molecular Orbital Theory for Metals
Caption
 Figure 21.7 Molecular orbital energy levels for Nan molecules. A crystal of sodium metal can be regarded as a giant Nan molecule, where n has a value of about 1020. As the value of n increases, the energy levels merge into an almost continuous band. Because each Na atom has one 3s valence electron and each MO can hold two electrons, the 3s band is half-filled. In this and subsequent figures, the deep red color denotes the filled portion of a band.
Notes
 Molecular orbital energy levels for sodium molecules.
Keywords
 molecular orbital theory, energy levels, sodium
21-08a, b
Title
 Molecular Orbital Theory for Metals
Caption
 Figure 21.8 Half-filled 3s band of MO energy levels for sodium metal. The direction of electron motion for the two degenerate sets of energy levels is indicated by the horizontal arrows. (a) In the absence of an electrical potential, the two sets of levels are equally populated, and no electric current flows through the wire. (b) In the presence of an electrical potential (positive electrode on the right), some of the electrons shift from one set of energy levels to the other, and there is a net current of electrons from left to right.
Notes
 Population of energy levels with and without the presence of an electrical potential.
Keywords
 molecular orbital theory, energy levels
21-09
Title
 Molecular Orbitals for Magnesium
Caption
 Figure 21.9 In magnesium metal, the 3s and 3p bands have similar energies and overlap to give a composite band consisting of four MOs per Mg atom. The composite band can accommodate eight electrons per Mg atom but is only partially filled, since each Mg atom has just two valence electrons. (In this and subsequent figures, the separate sets of energy levels for the right-and left-moving electrons aren’t shown.)
Notes
 Magnesium metal as a conductor.
Keywords
 molecular orbital theory, energy levels, magnesium
21-09-01UN
Title
 Worked Example 21.1
Caption
 The melting points of chromium and zinc are 1907°C and 420°C, respectively. Use band theory to account for the difference.
Notes
 Worked Example 21.1
Keywords
 band theory
21-09-02UN
Title
 Key Concept Problem 21.2
Caption
 The following pictures represent the electron population of the composite s-d band for three metals—Ag, Mo, and Y:
Notes
 Key Concept Problem 21.2
Keywords
 band theory
21-09-03UN
Title
 Key Concept Problem 21.3
Caption
 The following pictures represent the electron population of the composite s-d band for three metals—Hf, Pt, and Re:
Notes
 Key Concept Problem 21.3
Keywords
 band theory
21-10
Title
 Conductors, Insulators, and Semiconductors
Caption
 Figure 21.10 Bands of MO energy levels for (a) a metallic conductor, (b) an electrical insulator, and (c) a semiconductor. A metallic conductor has a partially filled band. An electrical insulator has a completely filled valence band and a completely empty conduction band, which are separated in energy by a large band gap. In a semiconductor, the band gap is smaller. As a result, the conduction band is partially occupied with a few electrons, and the valence band is partially empty. Electrical conductivity in metals and semiconductors results from the presence of partially filled bands.
Notes
 Molecular orbital energy levels corresponding to and distinguising conductors, insulators, and semiconductors.
Keywords
 molecular orbital theory, conductor, insulator, semiconductor
21-11
Title
 Doped Semiconductors
Caption
 Figure 21.11 MO energy levels for doped semiconductors. (a) An n-type semiconductor, such as silicon doped with phosphorus, has more electrons than needed for bonding and thus has negative electrons in the partially filled conduction band. (b) A p-type semiconductor, such as silicon doped with boron, has fewer electrons than needed for bonding and thus has vacancies—positive holes—in the valence band.
Notes
 Molecular orbital energy levels for doped semiconductors.
Keywords
 molecular orbital theory, doped semiconductor
21-11-02UN
Title
 Key Concept Problem 21.5
Caption
 The following pictures show the electron population of the bands of MO energy levels for four materials—diamond, silicon, silicon doped with aluminum, and white tin:
Notes
 Key Concept Problem 21.5
Keywords
 band theory, conductor, semiconductor
21-12
Title
 Superconductors
Caption
 Figure 21.12 The electrical resistance of mercury falls to zero at its superconducting transition temperature, Tc = 4.2 K. Above Tc, mercury is a metallic conductor: Its resistance increases (conductivity decreases) with increasing temperature. Below Tc, mercury is a superconductor.
Notes
 Electrical resistance of mercury with respect to temperature.
Keywords
 superconductor, mercury, temperature
21-14
Title
 Ceramic Superconductor
Caption
 Figure 21.14 One unit cell of the crystal structure of YBa2Cu3O7 contains one Y atom, two Ba atoms, three Cu atoms, and seven O atoms. In counting the Cu and O atoms, recall that the unit cell contains one-eighth of each corner atom, one-fourth of each edge atom, and one-half of each face atom (Section 10.8). The figure includes eight O atoms from neighboring unit cells to show the square pyramidal CuO5 groups and the square planar CuO4 groups.
Notes
 Crystal structure of the 1-2-3 compound YBa2Cu3O7 in which Cu has a fractional oxidation state of +2.33.
Keywords
 ceramic superconductor
21-16
Title
 Carbon-Based Conductors
Caption
 Figure 21.16 A portion of one unit cell of the face-centered cubic structure of K3C60 viewed perpendicular to a cube face. The C60 “buckyballs” are located at the cube corners and face centers, and the K+ions (red and blue spheres) are in two kinds of holes between the C603-ions. The K+ions shown in red lie in the plane of the cube face (the plane of the paper) and are surrounded octahedrally by six C603-ions. Those shown in blue lie in a plane one-fourth of a cell edge length below the plane of the paper and are surrounded tetrahedrally by four C603-ions.
Notes
 Face-centered cubic unit cell of K3C60 which is a metallic conductor at room temperature but becomes superconducting at 18 K.
Keywords
 carbon, superconductor, buckyball
21-17
Title
 Ceramics
Caption
 Figure 21.17 One unit cell of the cubic form of silicon carbide, SiC. The Si atoms are located at the corners and face centers of a face-centered cubic unit cell, while the C atoms occupy cavities (tetrahedral holes) between four Si atoms. Each C atom is bonded tetrahedrally to four Si atoms, and each Si atom is bonded tetrahedrally to four C atoms. The crystal can’t deform under stress because the bonds are strong and highly directional.
Notes
 Cubic unit cell of silicon carbide, a covalent network solid crystallizes in a diamond structure.
Keywords
 silicon carbide, ceramics
21-17-01UN
Title
 Formation of Titania
Caption
 High-purity, fine powders for ceramics can be made through the sol-gel method. In the synthesis of titania (TiO2), titanium(IV) chloride is treated with ethanol to form titanium(IV) ethoxide. The pure Ti(OCH2CH3)4 is then hydrolyzed with water to form Ti(OH)4, which can subsequently eliminate water molecules to form a three-dimensional network of oxygen-bridged titanium atoms.
Notes
 The sol-gel method for preparation of high-purity powders for ceramics.
Keywords
 sol-gel, ceramics, titania
21-18-040UN
Title
 Key Concept Summary
Caption
 Metals and solid-state materials key concept summary.
Notes
 Key Concept Summary for Chapter 21
Keywords
 key concept, summary
21-18-05UN
Title
 Key Concept Problem 21.12
Caption
 Look at the location of elements A, B, C, and D in the following periodic table. Predict whether these elements are likely to be found in nature as carbonates, oxides, sulfides, or in uncombined form. Explain.
Notes
 Key Concept Problem 21.12
Keywords
 key concept, minerals
21-18-06UN
Title
 Key Concept Problem 21.13
Caption
 Among the methods for extracting metals from their ores are (i) roasting a metal sulfide, (ii) chemical reduction of a metal oxide, and (iii) electrolysis.
Notes
 Key Concept Problem 21.13
Keywords
 key concept, metallurgy
21-18-07UN
Title
 Key Concept Problem 21.14
Caption
 The following pictures show the electron populations of the bands of MO energy levels for four different materials:
Notes
 Key Concept Problem 21.14
Keywords
 key concept, band theory, conductivity
21-18-08UN
Title
 Key Concept Problem 21.15
Caption
 The following pictures show the electron populations of the composite s-d bands for three different transition metals:
Notes
 Key Concept Problem 21.15
Keywords
 key concept, band theory, melting point
21-18-09UN
Title
 Key Concept Problem 21.16
Caption
 The following picture represents the electron population of the bands of MO energy levels for elemental silicon:
Notes
 Key Concept Problem 21.16
Keywords
 key concept, band theory, conductivity
21-18-10UN
Title
 Production of ferrochrome
Caption
 Ferrochrome, an iron-chromium alloy used to make stainless steel, is produced by reducing chromite with coke.
Notes
 Problem 21.34
Keywords
 metallurgy, ferrochrome
21-TB01
Title
 Table 21.1 Principal Ores of Some Important Metals
Caption
Notes
Keywords
21-TB03
Title
 Table 21.3 Band Gaps for the Group 4A Elements
Caption
Notes
Keywords
21-TB04
Title
 Table 21.4 Properties of Some Ceramic and Metallic Materials
Caption
Notes
Keywords
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