Group 17 elements standard potentials

Initially, the level of theory that provides accurate geometries and bond energies of TM compounds, yet allows calculations on medium-sized molecules to be performed with reasonable time and CPU resources, had to be determined. Systematic investigations of effective core potentials (ECPs) with different valence basis sets led us to propose a standard level of theory for calculations on TM elements, namely ECPs with valence basis sets of a DZP quality [9, 10]. The small-core ECPs by Hay and Wadt [11] has been chosen, where the original valence basis sets (55/5/N) were decontracted to (441/2111/N-11) withN = 5,4, and 3, for the first-, second-, and third-row TM elements, respectively. The ECPs of the second and third TM rows include scalar relativistic effects while the first-row ECPs are nonrelativistic [11], For main-group elements, either 6-31G(d) [12-16] all electron basis set or, for the heavier elements, ECPs with equivalent (31/31/1) valence basis sets [17] have been employed. This combination has become our standard basis set II, which is used in a majority of our calculations [18]. 

Symbol Cd atomic number 48 atomic weight 112.41 a Group IIB (Group 12) metallic element ionization potential 8.994eV electron configuration [Kr]4di°5s2 valence state +2 standard electrode potential, E° -0.40V. The isotopes and their natural relative abundance are ... 

Table 6.7 contains data for the Group 13 elements at pH values of 0 and 14, arranged in the form of Latimer-type diagrams for each element at the two pH values. The appropriate standard potentials appear between the two relevant oxidation states of the element. 

Use data from Fig. 1.39 and Appendix 2B to plot first ionization energy as a function of standard potential for the elements of Groups 1 and 2. What generalizations can be drawn from the graph ... 

All three elements in this group—Cu, Ag, and Au—are chemically rather inert, Ag more so than Cu, and Au more so than Ag. The standard potentials of their ions are all positive, in the order Au > Ag > Cu, so they are not readily oxidized. They have a common electron configuration, (n — 1 )d10nsi. 

The elements zinc, cadmium, and mercury, which have two electrons outside filled penultimate d shells, are classed in Group 12. Although the difference between the calcium and zinc subgroups is marked, zinc, and to a lesser extent cadmium, show some resemblance to beryllium or magnesium in their chemistry. We discuss these elements separately (Chapter 15), but note here that zinc, which has the lowest second ionization enthalpy in the Zn, Cd, Hg group, still has a value (1726 kJ mol-1) similar to that of beryllium (1757 kJ mol"1), and its standard potential (-0.76 V) is considerably less negative than that of magnesium. 

FIGURE 8-3 Ionization Energies of the Main Group Elements. (Data from C. E. Moore, Ionization Potentials and Ionization Limits Derived from the Analyses of Optical Spectra, National Standard Reference Data Series, U. S. National Bureau of Standards, NSRDS-NBS 34, Washington, DC, 1970.)... 

Thermodynamic data, chemical equilibria, and standard potentials, which should provide a useful source of information for the Group VI elements is contained in an excellent review. Another review of thermodynamic data has appeared which lists the heats of reaction and formation of molybdenum and tungsten oxides and halides, and some molybdates and tungstates. ... 

Figure 7.2 Trends in standard eiectrode potential and electronegativity x for elements in Groups 3 and 13.

The choice of the fill material initiating the discharge is very important. Together with a standard mercury fill it is often desirable to incorporate an additive in the fill material that has a low ionization potential [38, 39]. One category of low-ioniza-tion-potential materials is the group of alkali metals or their halides (Lil, Nal) but some other elements, such as Al, Ga, In, T1 [40, 41], Be, Mg, Ca, Sr, La, Pr, or Nd [23, 37, 42], can be used. 

Clearly the full potential of CIS PV devices has not been fully exploited, since the combination of group I-III-VI2 elements can result in a variety of end products. Therefore, standards need to be defined that can associate device processing, fabrication, and film composition to cell band gap and efficiency. Spray CVD in conjunction with SSP design provides a proof-of-concept for a reproducible highly manufacturable process. Items that need more investigation include (1) precursor design development of more volatile/thermally... 

The standard reduction potential for Be2+ is the least negative of the elements in the group and by the same token beryllium is the least electropositive and has the greatest tendency to form covalent bonds. The bulk metal is relatively inert at room temperature and is not attacked by air or water at high temperatures. Beryllium powder is somewhat more reactive. The metal is passivated by cold concentrated nitric acid but dissolves in both dilute acid and alkaline solutions with the evolution of dihydrogen. The metal reacts with halogens at 600°C to form the corresponding dihalides. 

---