Crystalline solid atomic solids

Know the five types of crystalline solid atomic, molecular, ionic, metallic, and network. 

Figure 4.5. Atomic Structure of Glass vs. Crystalline-Solid Atomic Structure.

In atomic crystalline solids, atoms are covalently bonded to each other. In covalent bonding, electrons are shared equally by the bonding atoms. 

All these works of art include an orderly arrangement of a particular object, similar to the arrangement of structural units in a crystalline solid atoms, ions, or molecules. 

This book should serve both as a state-of-art overview of what s going on in frontier areas (theoretical evaluation of noncovalent interactions, hydrogen-bonded crystals, coordination networks, solid-state reactivity and reactions taking place in the solid state, crystal polymorphism, etc.) and as an entry point to the fundamental methods and techniques required for a successful investigation of crystalline solids (crystallography, solid-state NMR spectroscopy, atomic force microscopy etc.). 

Crystalline solid. A solid that possesses rigid and long-range order its atoms, molecules, or ions occupy specific positions. (11.4)... 

Crystalline solids Ionic solids Molecular solids Atomic solids Electron sea model Alloy... 

Categories of crystalline solids Crystalline solids can be classified into five categories based on the types of particles they contain and how thoses particles are bonded together atomic solids, molecular solids, covalent network solids, ionic solids, and metallic solids. Table 12.5 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. 

Solids in which atoms are arranged in an orderly repeating pattern are called crystalline solids. These solids usually have flat surfaces, or faces, that make definite angles with one another. The orderly arrangements of atoms that produce these faces also cause the solids to have highly regular shapes ( FIGURE 12.2). Examples of crystalline solids include sodium chloride, quartz, and diamond. 

A FIGURE 3.5 Types of solid matter (a) In a crystalline solid, atoms or molecules occupy specific positions to create a well-ordered, three-dimensional structure, (b) In an amorphous solid, atoms do not have any long-range order. 

The properties of five types of crystalline solids—atomic, molecular, ionic, metallic, and network cova/ent—depend on the type(s) of particles in the crystal and the resultant interparticle forces. (Section 12.6)... 

The three-dimensional synnnetry that is present in the bulk of a crystalline solid is abruptly lost at the surface. In order to minimize the surface energy, the themiodynamically stable surface atomic structures of many materials differ considerably from the structure of the bulk. These materials are still crystalline at the surface, in that one can define a two-dimensional surface unit cell parallel to the surface, but the atomic positions in the unit cell differ from those of the bulk structure. Such a change in the local structure at the surface is called a reconstruction. 

Here is the distance between the molecule i in the gas phase (or, for a complex molecule, the centre of its atom i) and the centre of an atom j in the solid. If a particular face of a crystalline solid is being considered, the various values of r, can be expressed in terms of a single quantity z here z is the distance between the centre of the gas molecule (or a given atom or group thereof) and the plane through the centres of the atoms in the outermost layer of the solid. 

A crystalline solid is never perfect in that all of tire lattice sites are occupied in a regular manner, except, possibly, at the absolute zero of temperature in a perfect crystal. Point defects occur at temperatures above zero, of which the principal two forms are a vacant lattice site, and an interstitial atom which... 

In our discussion so far we have begged the question of just how the atoms in a solid move around when they diffuse. There are several ways in which this can happen. For simplicity, we shall talk only about crystalline solids, although diffusion occurs in amorphous solids as well, and in similar ways. 

To melt ice we have to put heat into the system. This increases the system entropy via eqn. (5.20). Physically, entropy represents disorder and eqn. (5.20) tells us that water is more disordered than ice. We would expect this anyway because the atoms in a liquid are arranged much more chaotically than they are in a crystalline solid. When water freezes, of course, heat leaves the system and the entropy decreases. 

EXAFS is a nondestructive, element-specific spectroscopic technique with application to all elements from lithium to uranium. It is employed as a direct probe of the atomic environment of an X-ray absorbing element and provides chemical bonding information. Although EXAFS is primarily used to determine the local structure of bulk solids (e.g., crystalline and amorphous materials), solid surfaces, and interfaces, its use is not limited to the solid state. As a structural tool, EXAFS complements the familiar X-ray diffraction technique, which is applicable only to crystalline solids. EXAFS provides an atomic-scale perspective about the X-ray absorbing element in terms of the numbers, types, and interatomic distances of neighboring atoms. 

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