Metals periodic trends

The usefulness of the main-group elements in materials is related to their properties, which can be predicted from periodic trends. For example, an s-block element has a low ionization energy, which means that its outermost electrons can easily be lost. An s-block element is therefore likely to be a reactive metal with all the characteristics that the name metal implies (Table 1.4, Fig. 1.60). Because ionization energies are... 

We begin this chapter by summarizing the major periodic trends exhibited by the t/block elements and their compounds. Then we describe some of the properties and key reactions of selected elements. The d-block metals form a wide variety of complexes and, in the second half of the chapter, we describe their structures and the two principal theories of their bonding. We end the chapter by examining the contribution of d-block elements to some important modern materials. 

The densities of transition metals also display regular periodic trends, as Figure 20-2b shows. Density increases moving down each column of the periodic table and increases smoothly across the first part of each row. 

Armentrout, R B., Kickel, B. L., 1996, Gas-Phase Thermochemistry of Transition Metal Ligand Systems Reassessment of Values and Periodic Trends in Organometallic Ion Chemistry, Freiser, B. S. (ed.), Kluwer, Amsterdam. 

Periodic variations in the surface tension of liquid metals, c1 , are shown in Figure 6.5. The much higher surface tension of rf-block metals compared to the s- and p-block metals suggests that the surface tension relates to the strength of interatomic bonding. Similar periodic trends can be found also for the melting temperature and the enthalpy of vaporization, and the surface tension of liquid metals is strongly... 

Periodic trends in ionization energy are linked to trends involving the reactivity of metals. In general, the chemical reactivity of metals increases down a group and decreases across a period. These trends, as well as a further trend from metallic to non-metallic properties across a period, and increasing metallic properties down a group, are shown in Table 3.1. 

The binary acids of non-metals exhibit periodic trends in their acid strength, as shown in Figure 8.5. Two factors are responsible for this trend the electronegativity of the atom that is bonded to hydrogen, and the strength of the bond. 

Marcus has tabulated AG° for a variety of ions, from water to a variety of solvents [34]. Values for the alkali metal ions (AGj (M+,w s)) are included in Table 7. AGj (Ag+, w CH3CN) are included for comparative purposes because the Ag/Ag+ couple is a reliable reference half-cell in a number of different solvents. AGj (H+, w s) are included because they are needed to determine the influence that pH might have on half-cells containing alkali metals. These numbers are also useful in revealing important periodic trends. To provide a frame of reference in comparing the various ions, entries in Table 7 are sorted by AG°(Na+, w s). 

A theoretical foundation for understanding these correlations is found in the calculated bulk electronic structures of the first- and second-row TMS. The electronic environment of the metal surrounded by six sulfur atoms in an octahedral configuration was calculated, using the hypotheses that all the sulfides could be represented by this symmetry as an approximation. There are several electronic factors that appear to be related to catalytic activity the orbital occupation of the HOMO (Highest Occupied Molecular Orbital), the degree of covalency of the metal-sulfur bond, and the metal-sulfur bond strength. These factors were incorporated into an activity parameter (A2), which correlates well with the periodic trends (Fig. 16) (74, 75). This parameter is equal to the product of the number of electrons contained in the... 

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,... 

The oxides of main-group elements show periodic trends in properties. Oxides of metals tend to be ionic and to form basic solutions in water. Oxides of nonmetals are molecular and the anhydrides of acids. 

FIGURE 19.2 Periodic trends in the properties of the main-group elements. The metallic elements (green) and the nonmetallic elements (lavender) are separated by the heavy stairstep line. The semimetals, shown in blue, lie along the line. 

The group 4A elements exemplify the increase in metallic character down a group in the periodic table Carbon is a nonmetal silicon and germanium are semimetals and tin and lead are metals. The usual periodic trends in atomic size, ionization energy, and electronegativity are evident in the data of Table 19.4. 

The group 6A elements are oxygen, sulfur, selenium, tellurium, and polonium. As shown in Table 19.7, their properties exhibit the usual periodic trends. Both oxygen and sulfur are typical nonmetals. Selenium and tellurium are primarily non-metallic in character, though the most stable allotrope of selenium, gray selenium, is a lustrous semiconducting solid. Tellurium is also a semiconductor and is usually classified as a semimetal. Polonium, a radioactive element that occurs in trace amounts in uranium ores, is a silvery white metal. 

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