Chemistry
Metallic Solids
Metallic solids are a type of solid material characterized by a lattice structure of positively charged metal ions surrounded by a sea of delocalized electrons. This electron sea allows metallic solids to conduct electricity and heat, and gives them their characteristic luster and malleability. Metallic solids are commonly used in various industrial applications due to their unique properties.
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10 Key excerpts on "Metallic Solids"
eBook - PDF- Kenneth S. Krane(Author)
- 2020(Publication Date)
- Wiley(Publisher)
Each of these solids has a characteristic color, texture, strength, hardness, or ductility; it has a certain measurable electrical conductivity, heat capacity, thermal conductivity, mag- netic susceptibility, and melting point; it has certain characteristic emission or absorption spectra in the visible, infrared, ultraviolet, or other regions of the electromagnetic spectrum. It is a fair generalization to say that all of these properties depend on two features of the structure of the material: the type of atoms or molecules of which the substance is made, and the way those atoms or molecules are joined or stacked together to make the solid. It is the formidable task of the solid-state (or condensed-matter) physicist or physical chemist to try to relate the structure of materials to their observed physical or chemical properties. Quantum mechanics plays a fundamental role in determining properties of the solid: mechanical, electrical, thermal, magnetic, optical, and so forth. In this chapter, we illustrate the application of quantum mechanics to the study of solids by studying some of their thermal, electrical, and magnetic properties. 11.1 CRYSTAL STRUCTURES Our discussion will concentrate on materials in which the atoms or molecules occupy regular or periodic sites; this structure is called a lattice, and materi- als with this structure are called crystals. Crystalline materials include many metals, chemical salts, and semiconductors. One property that distinguishes crystals is their long-range order—once we begin constructing the lattice in one location, we determine the placement of atoms that are quite far away. In this respect, the crystal is like a brick wall, in which the bricks are stacked in a periodic array and the placement of a brick is predetermined by the original arrangement of bricks far away compared with the size of a brick.
eBook - PDFMaterials Principles and Practice
Electronic Materials Manufacturing with Materials Structural Materials
- Charles Newey, Graham Weaver(Authors)
- 2013(Publication Date)
- Butterworth-Heinemann(Publisher)
The electrons don't 'know' to which atom they 'belong' so we might expect them to move through this continuum from atom to atom; such delocalization allows the possibility of electrical conduction — a conspicuous property of all metals. See TElectrical conduction▲ But the metallic bond is more than just a transitory covalent bond. If the outer electrons are delocalized from their parent nuclei the crystal lattice is one of like positive ions. It is held together by the 'paste' of delocalized electrons. Although the ions repel each other the fluidity of the electronic glue allows considerable movement of ions without great energy cost. Ductility is another characteristic of metals. A better image of the metallic bond comes from considering more generally the simultaneous interaction of many atoms with their outer electrons. From this we can develop a view of electrons in solids, whether in a metallic conductor or in a covalent insulator. fuzzy s state Figure 3.44 Overlapping s states 140 3.8.3 Electrons in solids Using quantum mechanics, solid state physicists have given a much more powerful description of electrons associated with many atoms. This is the so-called 'band theory' which goes beyond metals to all solids and lets us model all properties determined by electrons. The most direct experimental evidence of the nature of the 'disturbed' electron states around densely-packed (solid) atoms comes from X-ray studies. See TX-rays and energy bands A The principle of the necessary quantum mechanical calculation is to find the electron energy states for one atom with other atoms set around it in the appropriate directions to make a chosen (crystal) structure. The problem is to imagine a way of representing the influence of the surroundings which is both accurate enough for the results to mean something and simple enough to allow us to do the sums.
eBook - PDF- Young, William Vining, Roberta Day, Beatrice Botch(Authors)
- 2017(Publication Date)
- Cengage Learning EMEA(Publisher)
AlbertSmirnov/iStockphoto.com 13 The Solid State Unit Outline 13.1 Introduction to Solids 13.2 Metallic Solids 13.3 Ionic Solids 13.4 Bonding in Metallic and Ionic Solids 13.5 Phase Diagrams In This Unit… In Intermolecular Forces and the Liquid State (Unit 12), we focused on intermolecular forces, the non bonding interactions between collections of atoms and molecules, and how these forces manifest themselves in the physical properties of liquids. In this unit we continue this explora-tion with the study of structure and bonding in solids. We begin by look-ing at the structural features of some simple types of solids. Then we investigate bonding in different types of solids, and conclude by tying the three states of matter together in what is known as a phase diagram. © Vladmir Fedorchuk/Fotolia.com Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-300 Unit 13 The Solid State 372 13.1 Introduction to Solids 13.1a Types of Solids Most solids are best described as either crystalline or amorphous. A crystalline solid is one in which the particles in the solid are arranged in a regular way. There is long-range order extending over the entire crystal, which can be described as repeating atomic- or molecular-level building blocks. The atomic-level order in a crystalline solid is often reflected in the well-defined faces of the crystal. Examples of pure substances that are crys-talline solids at room temperature and pressure are diamond, table salt (NaCl) , and sugar (C 12 H 22 O 11 ) . In an amorphous solid , the particles that make up the solid are arranged in an irregular manner and the solid lacks long-range order. Many important solid materials, such as synthetic fibers, plastics, and glasses, are amorphous, but pure solid substances, such as elemental phosphorus or sulfur, may also exist in amorphous forms.
eBook - PDFChemistry
Structure and Dynamics
- James N. Spencer, George M. Bodner, Lyman H. Rickard(Authors)
- 2011(Publication Date)
- Wiley(Publisher)
The elements along the dividing line are called semimetals or metalloids and have properties between those of metals and nonmetals. The semimetals can be found on the bond-type triangle in Figure 9.1 in the region between Al and As. Because these elements lie between those that conduct electricity, on one hand, and those that are insulators, on the other, they often form semiconductors. 9.11 Ionic Solids Ionic solids are salts, such as NaCl, that form an extended three-dimensional net- work of ions held together by the strong force of attraction between ions of oppo- site charge, as shown in Figure 9.18. The structures of six ionic solids are shown in Figure 9.19. Other compounds are often described in terms of one of these structures. The magnetic oxide tapes that were once used to record music, for example, contain CrO 2 , which has a structure similar to that of TiO 2 shown in Figure 9.19. Because the force of attraction depends inversely on the square of the dis- tance between the positive and negative charges, the strength of an ionic bond depends inversely on the size of the ions that form the solid. When the ions are large, the bond is relatively weak. But the ionic bond is still strong enough to ensure that salts have relatively high melting points and boiling points. Sodium chloride, for example, melts at 801°C and boils at 1413°C. These solids are often brittle, however, easily breaking into smaller parts when hit with a hammer. Solids retain their shape, are difficult to compress, and are denser than liq- uids and gases. These characteristic properties suggest that solids contain parti- cles that are packed as tightly as possible. Ionic compounds form solids in which the force of attraction between the ions of opposite charge is maximized by keep- ing the ions as close together as possible. Ionic solids are located in the ionic region of a bond-type triangle as shown in Figure 9.1.
eBook - PDFElectrical Conduction in Solid Materials
Physicochemical Bases and Possible Applications
- J. P. Suchet, B. R. Pamplin(Authors)
- 2013(Publication Date)
- Pergamon(Publisher)
Pari I Physicochemical Bases This page intentionally left blank Chapter 1 Conductors 1.1. Interatomic bonds A solid phase contains a very large number of atoms, all identical in the case of an element, or of several different kinds in the case of an alloy or chemical compound. These atoms are linked with one another by means of their electrons on which cohesion of the solid depends. But these bonds can be of several different types, depending a great deal on the total ionization energies of the atoms present, in other words the energies needed to move all the valency electrons of these atoms to infinity. For an atom of a given element, the term of this operation is a positively charged ion, the electronic formula of which is that of the rare gas preceding the element in the Periodic Table of Elements. Table 1.1 gives these energies in electron volts for the main elements. Atoms for elements which have low numbers (less than about 35) on this table combine with one another in the form of compact stacks of spheres, and part of their valency electrons escapes from the attraction of their nuclei, forming a gas of delocalized electrons ready to move in an electric field. This is the metallic bond, to be found in metals and alloys, where it gives rise to chemical formulae, the lower indices of which are usually neither simple nor unique for a given association of elements. Electrical conduction of phases with this type of bond is naturally high, and entirely due to the delocalized electron gas. When one solid phase contains atoms of elements for which the numbers in Table 1.1 are in some cases lower and in other cases higher than 35, atoms in elements with numbers above 35 do not lose their electrons but tend to complete their electronic valency octet at the ex-pense of atoms of elements with numbers below 35, thus attaining the 3
eBook - PDF- David Halliday, Robert Resnick, Jearl Walker(Authors)
- 2018(Publication Date)
- Wiley(Publisher)
Let’s start by char- acterizing conducting and nonconducting materials. The Electrical Properties of Solids We shall examine only crystalline solids — that is, solids whose atoms are arranged in a repetitive three-dimensional structure called a lattice. We shall not consider such solids as wood, plastic, glass, and rubber, whose atoms are not arranged in such repetitive patterns. Figure 41-1 shows the basic repetitive units (the unit cells) of the lattice structures of copper, our prototype of a metal, and silicon and dia- mond (carbon), our prototypes of a semiconductor and an insulator, respectively. We can classify solids electrically according to three basic properties: 1. Their resistivity ρ at room temperature, with the SI unit ohm-meter (Ω · m); resistivity is defined in Module 26-3. 2. Their temperature coefficient of resistivity α, defined as α = (1/ρ)( dρ/dT) in Eq. 26-17 and having the SI unit inverse kelvin (K –1 ). We can evaluate α for any solid by measuring ρ over a range of temperatures. 3. Their number density of charge carriers n. This quantity, the number of charge carriers per unit volume, can be found from measurements of the Hall effect, as discussed in Module 28-3, and has the SI unit inverse cubic meter (m –3 ). From measurements of resistivity, we find that there are some materials, insulators, that do not conduct electricity at all. These are materials with very high resistivity. Diamond, an excellent example, has a resistivity greater than that of copper by the enormous factor of about 10 24 . We can then use measurements of ρ, α, and n to divide most noninsulators, at least at low temperatures, into two categories: metals and semiconductors. Semiconductors have a considerably greater resistivity ρ than metals. Semiconductors have a temperature coefficient of resistivity α that is both high and negative. That is, the resistivity of a semiconductor decreases with tem- perature, whereas that of a metal increases.
eBook - PDF- Efthimios Kaxiras, John D. Joannopoulos(Authors)
- 2019(Publication Date)
- Cambridge University Press(Publisher)
1 From Atoms to Solids Materials exhibit an extremely wide range of properties, which is what makes them so useful and indispensable to humankind. The extremely wide range of the properties of materials is surprising, because most of them are made up from a relatively small subset of the elements in the Periodic Table: about 20 or 30 elements, out of more than 100 total, are encountered in most common materials. Moreover, most materials contain only very few of these elements, from one to half a dozen or so. Despite this relative simplicity in composition, materials exhibit a huge variety of properties over ranges that differ by many orders of magnitude. It is quite extraordinary that even among materials composed of single elements, physical properties can differ by many orders of magnitude. One example is the ability of materials to conduct electricity. What is actually measured in experiments is the resistivity, that is, the difficulty with which electrical current passes through a material. Some typical single-element Metallic Solids (like Ag, Cu, Al) have room-temperature resistivities of 1–5 μ·cm, while some metallic alloys (like nichrome) have resistivities of 10 2 μ·cm. All these materials are considered good conductors of electrical current. Certain single-element solids (like Si and Ge) have room-temperature resistivities much higher than good conductors, for instance, 2.3 × 10 11 μ·cm for Si, and they are considered semiconductors. Finally, certain common materials like wood (with a rather complex structure and chemical composition) or quartz (with a rather simple structure and composed of two elements, Si and O) have room-temperature resistivities of 10 16 –10 19 μ·cm (for wood) to 10 25 μ·cm (for quartz). These solids are considered insulators. The range of electrical resistivities covers an impressive 25 orders of magnitude.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Library Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 4 Solid-state Physics Solid-state physics is the study of rigid matter, or solids, through methods such as quantum mechanics, crystallography, electromagnetism and metallurgy. It is the largest branch of condensed matter physics. Solid-state physics studies how the large-scale properties of solid materials result from their atomic-scale properties. Thus, solid-state physics forms the theoretical basis of materials science. It also has direct applications, for example in the technology of transistors and semiconductors. Introduction Solid materials are formed from densely-packed atoms, with intense interaction forces between them. These interactions are responsible for the mechanical (e.g. hardness and elasticity), thermal, electrical, magnetic and optical properties of solids. Depending on the material involved and the conditions in which it was formed, the atoms may be arranged in a regular, geometric pattern (crystalline solids, which include metals and ordinary water ice) or irregularly (an amorphous solid such as common window glass). The bulk of solid-state physics theory and research is focused on crystals, largely because the periodicity of atoms in a crystal — its defining characteristic — facilitates mathe-matical modeling, and also because crystalline materials often have electrical, magnetic, optical, or mechanical properties that can be exploited for engineering purposes. The forces between the atoms in a crystal can take a variety of forms. For example, in a crystal of sodium chloride (common salt), the crystal is made up of ionic sodium and chlorine, and held together with ionic bonds. In others, the atoms share electrons and form covalent bonds. In metals, electrons are shared amongst the whole crystal in metallic bonding. Finally, the noble gases do not undergo any of these types of bonding.
eBook - PDF- Hasse Fredriksson, Ulla Åkerlind(Authors)
- 2008(Publication Date)
- Wiley(Publisher)
A cluster in a pure metal melt may be assumed to be a stable unit consisting of a central atom surrounded by the number of atoms, which corresponds to the coordination number Z coord , characteristic of the type of atoms in question. The interatomic forces between the atoms inside a cluster may be strong but weaker than the forces between the atoms in the corresponding solid metal. If the forces between the clusters are assumed to be weak, the ability of the melt to adapt its shape to the shape of the container can easily be explained. 406 Physics of Functional Materials However, no theory which discusses the properties of liquids and melts in terms of clusters has been developed yet and there is no experimental evidence which proves the existence of clusters so far, other then the short-range order observed by the X-ray analysis, especially in binary alloys. The fundamental problem with the theory of liquids and melts is the difficulty of expressing the positions of the atoms as a function of time. This topic is briefly discussed in connection with the theory of heat capacity of liquids on page 412. 8.4 Melting Points of Solid Metals At a given pressure, the melting point of an element is the only temperature at which the element can exist in stable form both as a solid and a liquid. Table 8.3 shows that the melting points of metals vary widely, and change slightly with pressure. They depend on the structure of the crystal lattice of the metal and the strength of the interatomic forces. All matter is in constant motion. In the solid state, the atoms are not fixed to their exact sites in the crystal lattice. The sites are the centre of the atomic vibrations. At the melting point the vibration energy is larger than the binding energy and the crystal structure splits up.
eBook - PDFElectrons, Neutrons and Protons in Engineering
A Study of Engineering Materials and Processes Whose Characteristics May Be Explained by Considering the Behavior of Small Particles When Grouped Into Systems Such as Nuclei, Atoms, Gases, and Crystals
- J. R. Eaton(Author)
- 2013(Publication Date)
- Pergamon(Publisher)
CHAPTER 17 ELECTRICAL CONDUCTION IN SOLIDS INTRODUCTION The study of the microscopic properties of materials has led to an improved knowledge of the mechanism of electrical conduction in solids. The theory which has explained the electrical properties of metals and of insulators has opened the way to some spectacular developments in that intermediate class of materials known as semi-conductors. In fact, the theory has been so firmly es-tablished that the useful properties of certain of these materials were predicted well before methods were devised to produce the materials themselves. As a result of the developments in solid state science, there are now available semi-conductor devices which will perform the functions of many of the types of vacuum tubes, with improved characteristics and with lower cost. In addition, many new applications provide means for electric circuit control which are proving to be of increasing commercial and scientific importance. TABLE 17.1. RESISTIVITY OF MATERIALS 20°C (ohm-cm) Metals Semiconductors Insulators Silver Copper Aluminum Graphite Germanium Silicon Mica Quartz Diamond 1.6 X 10-6 1.7 X 10-6 2.8 X 10-6 6 x 10-3 3Χ 10-3 tol00 3 X 10-4 to 10 4 9 X 1 0 1 4 3X 10 16 5X 10 15 An exact explanation of the electrical properties of solids is to be found in the mathematical methods of wave mechanics. It is fortunate, however, that many of the basic principles of electric conduction may be explained on the basis of relatively simple theory. A discussion at this level leads to an insight into the processes involved and permits at least a partial understanding of the develop-ments of the mathematical physicist. The theory presents an explanation of the very great range of the resistivity of the materials of engineering, typical examples of which are shown in Table 17.1. Note that silver and copper have a resistivity of approximately 1 x 10~ 6 ohm-cm 312
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