Metallic behavior, trends

In the preceding chapter we looked at the elements of the third row in the periodic table to see what systematic changes occur in properties when electrons are added to the outer orbitals of the atom. We saw that there was a decided trend from metallic behavior to nonmetallic, from base-forming to acid-forming, from simple ionic compounds to simple molecular compounds. These trends are conveniently discussed... 

Tellurium (m.p. 450 °C, density 6.25 g cm-3) is more metallic in its appearance, but it is not a good electrical conductor as are most metals. Polonium, on the other hand, is typically metallic in its electrical properties. Selenium and tellurium are best regarded as semiconductors, and sulfur is nonmetallic in behavior (an insulator). Thus, the usual trend from nonmetallic to metallic behavior is shown in going down Group VIA of the periodic table. All of these elements differ substantially from oxygen in their chemical properties. 

Trends in Metallic Behavior Properties of Monatomic Ions... 

Describe the general properties of metals and nonmetals and understand how trends in metallic behavior relate to ion formation, oxide acidity, and magnetic behavior understand the relation between atomic and ionic size and write ion electron configurations ( 8.5) (SPs 8.6-8.8) (EPs 8.47-8.65)... 

Write electron configurations of transition metal atoms and ions compare periodic trends in atomic properties of transition elements with those of main-group elements explain why transition elements have multiple oxidation states, how their metallic behavior (type of bonding and oxide acidity) changes with oxidation state, and why many of their compounds are colored and paramagnetic ( 22.1) (SP 22.1) (EPS 22.1 -22.17)... 

Because atoms get larger down a group, metallic behavior (such as ability to form cations and basicity of oxides) inaeases, and this trend becomes especially apparent in Groups 3A(13) to 6A(16). 

Trends in Metallic Behavior 265 Properties of Monatomic Ions 266 CHAPTER REVIEW GUIDE 271 PROBLEMS 272... 

Electrocatalysis of the ORR of various Chevrel type chalcogenide compounds was first studied by Alonso-Vante and Tributsch [19] in an acid medium and an enhancement in the ORR activity was observed when Mo was partially substituted by Ru. The compounds containing non-substituted octahedral Mo show metallic behavior while Ru substituted Mo octahedral (Moe-rM Xg, where X = S, Se, Te) systems show semiconducting behavior. The compound Mo4.2Rui,8Se8 displayed catalytic behavior comparable to that of Pt. The ORR overpotentials on catalysts of the series MogXg followed the trend Te[Pg.468]

The diffusion of metal ions in vitreous siUca has not been studied as extensively as that of the gaseous species. The alkaU metals have received the most attention because their behavior is important in electrical appHcations. The diffusion coefficients for various metal ions are Hsted in Table 5. The general trend is for the diffusion coefficient to increase with larger ionic sizes and higher valences. 

Within the general trend in the behavior across the actinide series, their alloys, and their metallic compounds from superconductors to local moment magnets, the only serious irregularity occurs in some plutonium compounds. These compounds should be magnetic but turn out to be temperature independent paramagnets. 

Capacitance data for various crystal faces are available for Bi and Sb.28 As a broad trend, the faces with more negative values of Eam0 show higher values of C. Although this is qualitatively in line with the behavior of real Ag surfaces, the response of Bi and Sb is complicated by their semimetal nature, which gives rise to space-charge effects. For this reason it is not straightforward to compare the absolute values of C and their crystal face sequences with those of metals. 

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