Ionic bonding periodic trends

If we examine the distances listed in Table 7.2 some interesting facts emerge. For a given metal A. the A—P distance is constant as we might expect for an ionic alkaline earth metal-phosphide bond. Furthermore, these distances increase calcium < strontium < barium in increments of about 15 pm os do the ionic radii of Ca2+. St7, and Ba- (Table 4.4). However, the B—P distances vary somewhat more with no periodic trends (Mn. Cu larger Ni, Fe, Co smaller). Most interesting, however, is the huger variability in the P—P distance from about 380 pm (Mn. Fe) to 225 pm (Cu). As it Luros Out, the lower limit of 225 pm (Cu) is a typical value for a P— P bond (Table E.l,... 

For example, hydrogen chloride, also known as hydrochloric acid, has a low melting point and a low boiling point. (It is a gas at room temperature.) These properties might lead you to believe that hydrogen chloride is a covalent compound. Hydrogen chloride, however, is extremely soluble in water, and the water solution conducts electricity. These properties are characteristic of an ionic compound. Is there a clear, theoretical way to decide whether the bond between hydrogen and chlorine is ionic or covalent The answer lies in a periodic trend. 

The chemical formula NaCl does not explicitly indicate the ionic nature of the compound, only the ratio of ions. Furthermore, values of electronegativities are not always available. So we must learn to recognize, from positions of elements in the periodic table and known trends in electronegativity, when the difference in electronegativity is large enough to favor ionic bonding. 

E2.10 Table 2.7 lists selected covalent radii of the main group elements. As we can see from the table, the trends in covalent radii follow closely the trends in atomic and ionic radii covered in Chapter 1 (Section L7(a)). Considering first the horizontal periodic trends we can see that the single bond covalent radii decrease if we move horizontally from left to right in the periodic table. Recall that the atomic radii decrease while the increases in... 

Types of Bonding Three Ways Metals and Nonmetals Combine 277 Lewis Symbols and the Octet Rule 278 The Ionic Bonding Model 280 Why Ionic Compounds Form The Importance of Lattice Energy 280 Periodic Trends in Lattice Energy 281 How the Model Explains the Properties of Ionic Corrpounds 283... 

Other compounds. Hydrides and fluorides of elements 119 and 120 were considered within the PP and ab initio DF approximations [245, 265, 266], It was shown that bond distances decrease from the 7th to the 8th period for group-1 and 2 elements due to the relativistic ns AO contraction. The 119F was found to be less ionic than lighter alkaline fluoride homologs in contrast to the expectations based on the periodic trends. 

This chapter and the remaining chapters offer many opportunities to relate new information to principles presented earlier in the text. Ideas of atomic structure, periodic trends in atomic and ionic radii, chemical bonding, and thermodynamics will help us to understand the chemical behavior of the... 

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