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Chemical Bonding in Condensed Phases

Wai-Kee Li, Gong-Du Zhou, and Thomas Chung Wai Mak

in Advanced Structural Inorganic Chemistry

This chapter starts off with the classification of solids, then discusses the various types of bonding or interaction in solids, including ionic bonding, metallic bonding, covalent bonding (band ... More

This chapter starts off with the classification of solids, then discusses the various types of bonding or interaction in solids, including ionic bonding, metallic bonding, covalent bonding (band theory), and van der Waals interaction. Numerous examples are given for each type of bonding.Less

Gaseous alkali metal halides: ionic bonds

Arne Haaland

in Molecules and Models: The molecular structures of main group element compounds

The evaporation of an alkali metal halide (MX) yields a mixture of monomers and smaller amounts of dimers, trimers, and tetramers. This chapter describes the monomers in terms of their electric ... More

The evaporation of an alkali metal halide (MX) yields a mixture of monomers and smaller amounts of dimers, trimers, and tetramers. This chapter describes the monomers in terms of their electric dipole moments, dissociation energies, and bond distances. The spherical ion model is used to construct potential energy curves and to calculate dissociation energies in reasonable agreement with their experimental counterparts from the experimental bond distances. Similar calculations on the dimers and on crystals with rock salt structure indicate that the M-X bond distances should be 5% and 15%, respectively, longer than in the monomers. The polarizable ion model leads to significantly better agreement between experimental and calculated electric dipole moments than the spherical ion model. Finally, the crystal structures of compounds containing a negatively charge alkali metal atom or even an isolated electron as cations are described.Less

Cation coordination number

I. David Brown

in The Chemical Bond in Inorganic Chemistry: The Bond Valence Model

Traditionally, coordination numbers have been predicted using ionic radius ratios, but this takes no account of the softness of the repulsion between the ligands. Oxygen ions are drawn closer if they ... More

Traditionally, coordination numbers have been predicted using ionic radius ratios, but this takes no account of the softness of the repulsion between the ligands. Oxygen ions are drawn closer if they form strong bonds to a common cation, e.g. N5+ compared to Mg2+ or Al3+. The O-O distance depends on the component of the valence of the cation-O bonds along the O-O direction. Other factors that determine coordination number are the softness of the cation, and deviations from valence matching.Less

Solvated Ions in Water

Bruce C. Bunker and William H. Casey

in The Aqueous Chemistry of Oxides

In most undergraduate chemistry classes, students are taught to consider reactions in which cations and anions dissolved in water are depicted as isolated ions. For example, the magnesium ion is ... More

In most undergraduate chemistry classes, students are taught to consider reactions in which cations and anions dissolved in water are depicted as isolated ions. For example, the magnesium ion is depicted as Mg2+, or at best Mg2+(aq). For anions, these descriptions may be adequate (if not accurate). However, for cations, these abbreviations almost always fail to describe the critical chemical attributes of the dissolved species. A much more meaningful description of Mg2+ dissolved in water is [Mg(H2O)6]2+, because Mg2+ in water does not behave like a bare Mg2+ ion, nor do the waters coordinated to the Mg2+ behave anything like water molecules in the bulk fluid. In many respects, the [Mg(H2O)6]2+ ion acts like a dissolved molecular species. In this chapter, we discuss the simple solvation of anions and cations as a prelude to exploring more complex reactions of soluble oxide precursors called hydrolysis products. The two key classes of water–oxide reactions introduced here are acid–base and ligand exchange. First, consider how simple anions modify the structure and properties of water. As discussed in Chapter 3, water is a dynamic and highly fluxional “oxide” containing transient rings and clusters based on tetrahedral oxygen anions held together by linear hydrogen bonds. Simple halide ions can insert into this structure by occupying sites that would normally be occupied by other water molecules because they have radii (ranging from 0.13 to 0.22 nm in the series from F- to I-) that are comparable to that of the O2- ion (0.14 nm). Such substitution is clearly seen in the structures of ionic clathrate hydrates, where the anion can replace one and sometimes even two water molecules. Larger anions can also replace water molecules within clathrate hydrate cages. For example, carboxylate hydrate structures incorporate the carboxylate group within the water framework whereas the hydrophobic hydrocarbon “tails” occupy a cavity within the water framework, as in methane hydrate (see Chapter 3). Water molecules form hydrogen bonds to dissolved halide ions just as they can to other water molecules, as designated by OH-Y-. Less

An Overview of Oxide Structures and Compositions

Bruce C. Bunker and William H. Casey

in Title Pages

This entire book is devoted to exploring the chemistry of compounds that contain one simple anion: the O2-ion. Except under high-vacuum conditions (see Chapter 6), the species in oxides that ... More

This entire book is devoted to exploring the chemistry of compounds that contain one simple anion: the O2-ion. Except under high-vacuum conditions (see Chapter 6), the species in oxides that interact with water and other environmental chemicals are O2- ions, because the charge-compensating cations are invariably buried beneath an oxide surface layer. One might wonder how we can fill an entire volume discussing the chemical interactions between this single anion and a single chemical: the water molecule. The single most important concept that must be appreciated to understand the contents of this book is that the chemistry and properties of O2- anions are critically dependent on all the cations to which the O2- ions are bound. Each bound cation modifies the electron distributions around the O2- site, changing its local charge, local bonding configurations, acid–base chemistry, ion exchange chemistry, electrochemical properties, chemical stability, and electrical and optical properties. None of these changes are subtle, and in fact most oxide properties are staggering in their diversity. Before considering the chemistry of oxides, it is important to gain an appreciation of just how diverse the structures of oxide materials really are. As this introduction makes clear, there is no such thing as a single, simple O2- ion. There are a myriad of different O2- sites found in the oxides that we encounter often in our daily lives, each of which exhibits its own unique properties. The purpose of this book is to provide a framework that can be used to predict, rationalize, and exploit the rich chemistry associated with those sites. The number of different structures and compositions that can be generated for oxides is almost limitless. The O2- ion forms compounds with more than 90 elements in the Periodic Table that are capable of losing electrons to form cations. The oxide anion combines with cations with charges that range from +1 to +7. Many elements exhibit more than one stable oxidation state, pushing the total number of chemically distinct cations with which O2- can interact to well more than 120. Less

Bioinorganic Chemistry

Wai-Kee Li, Hung Kay Lee, Dennis Kee Pui Ng, Yu-San Cheung, Kendrew Kin Wah Mak, and Thomas Chung Wai Mak

in Problems in Structural Inorganic Chemistry

This chapter presents 19 problems covering the subject of bioinorganic chemistry, along with their corresponding solutions.