A Survey of the Representative Elements

The traditional form of the periodic table is shown in Fig. 18.1. Recall that the representative elements, whose chemical properties are determined by the valence-level s and p electrons, are designated Groups lA through 8A. The transition metals, in the center of the table, result from the filling of d orbitals. The elements that correspond to the filling of the 4/and 5/ orbitals are listed separately as the lanthanides and actinides, respectively. 

The heavy black line in Fig. 18.1 separates the metals from the nonmetals, except for one case. Hydrogen, which appears on the metal side, is a non-metal. Some elements just on either side of this line, such as silicon and germanium, exhibit both metallic and nonmetallic properties. These elements are often called metalloids, or semimetals. The fundamental chemical difference between metals and nonmetals is that metals tend to lose their valence electrons to form cations, which usually have the valence electron configuration 

The periodic table. The elements in the A groups are the representative elements. The elements shown in pink are called transition metals. The heavy black line approximately separates the nonmetals from the metals. The elements that have both metallic and nonmetallic properties (semimetals) are shaded in blue. 

Metallic character inaeases going down a group in the periodic table. 

The structure of quartz, which has the empirical formula SiOj. Note that the structure is based on interlocking Si04 tetrahedra, in which each oxygen atom is shared by two silicon atoms. 

Unless otherwise noted, all art on this pag is Cengage Learning 2014. 

The effect of size is also evident in other groups. For example, the oxides of the metals in Group 2A are all quite basic except for the first member of the series beryllium oxide (BeO) is amphoteric. The basicity of an oxide depends on its ionic 

In Group 4A the effect of size is reflected in the dramatic differences between the chemical properties of carbon and silicon. The chemistry of carbon is dominated by molecules containing chains of C—C bonds, but silicon compounds mainly contain Si—O bonds rather than Si—Si bonds. Silicon does form compounds with chains of Si—Si bonds, but these compounds are much more reactive than the corresponding carbon compounds. The reasons for the difference in reactivity between the carbon and siUcon compounds are quite complex but are likely related to the differences in the sizes of the carbon and silicon atoms. 

---

For the first time in our survey of the representative elements, we encounter several that were known to the ancients. Carbon, tin, and lead have been known in elemental form for thousands of years. In the 1820s, silicon was isolated by reduction of the fluoride with potassium, while germanium (Mendeleev s eka-silicon) was found in a silver ore some 60 years later. 

This book offers no solutions to such severe problems. It consists of a review of the inorganic chemistry of the elements in all their oxidation states in an aqueous environment. Chapters 1 and 2 deal with the properties of liquid water and the hydration of ions. Acids and bases, hydrolysis and solubility are the main topics of Chapter 3. Chapters 4 and 5 deal with aspects of ionic form and stability in aqueous conditions. Chapters 6 (s- and p-block). 7 (d-block) and 8 (f-block) represent a survey of the aqueous chemistry of the elements of the Periodic Table. The chapters from 4 to 8 could form a separate course in the study of the periodicity of the chemistry of the elements in aqueous solution, chapters 4 and 5 giving the necessary thermodynamic background. A more extensive course, or possibly a second course, would include the very detailed treatment of enthalpies and entropies of hydration of ions, acids and bases, hydrolysis and solubility. 

Figure 5.5 Survey of the symmetry properties for selected types of homo- and heterodimers of tetra-urea calix[4]arenes, represented by squares with the phenolic units (A, B) on the corners. Symmetry elements and symmetry classes (with and without directionality of the hydrogen bonds, shown by arrows) are indicated.

C.E. Miller and C.S. Henriquez. Finite element analysis of bioelectric phenomena. Crit. Rev. Biomed. Eng., 18 181-205,1990. This represents the first review paper on the use of the finite element method as applied to biomedical problems. As the authors note, bioengineers came to these methods only fairly recently, as compared to other engineers. It contains a good survey of applications. 

The purpose of the detailed survey is to ensure a cost-effective repair in line with the client s requirements. This is done by accurately defining and measuring the cause, extent and severity of deterioration. In Chapter 7, we will discuss how test measurements may be used to model the deterioration rate, time to corrosion and life cycle costing. We will need to know how much damage has been done and what has caused the damage. Quantities for repair tenders will probably be based on the results of this survey, so a full survey of all affected elements may be required. Alternatively a full visual survey may be required, with a hammer (delamination) survey of all accessible locations. A number of representative areas may be selected for a detailed survey of cover depths, carbonation depths, chloride content or profile, half cell potentials and other techniques described in the following sections of this chapter. 

---