The s Block Metals

The saline carbides are formed most commonly from the metals of Groups 1 and 2, aluminum, and a few other metals. The s-block metals form saline carbides when their oxides are heated with carbon. The anions present in saline carbides are either C>2 or C4. All the C4 carbides, which are called methides, produce methane and the corresponding hydroxide in water ... 

The s-block metals have low ionization energies, which enables them to easily lose electrons in chemical reactions. 

The transition metals lie in the d block, at the center of the periodic table, between the s-block metals and the elements in the p block, as Figure 20-1 shows. As we describe in Chapter 8, most transition metal atoms in the gas phase have valence electron configurations of, where x is the group number of the metal. Titanium, for... 

FIGURE 21.2 Primary mineral sources of metals. The s-block metals occur as chlorides, silicates, and carbonates. The d- and p-block metals are found as oxides and sulfides, except for the group 3B metals, which occur as phosphates, and the platinum-group metals and gold, which occur in uncombined form. There is no mineral source of technetium (Tc in group 7B), a radioactive element that is made in nuclear reactors. 

We might also expect to find oxide ores for the s-block metals and sulfide ores for the more electronegative p-block metals. In fact, sulfide ores are common for the p-block metals, except for A1 and Sn, but oxides of the s-block metals are strongly basic and far too reactive to exist in an environment that contains acidic oxides such as CO2 and SiC>2. Consequently, s-block metals are found in nature as carbonates, as silicates, and, in the case of Na and K, as chlorides (Sections 6.7 and 6.8). Only gold and the platinum-group metals (Ru, Os, Rh, Ir, Pd, and Pt) are sufficiently unreactive to occur commonly in uncombined form as the free metals. 

Question 1.1 Using the information you have been given in Section 1.2, draw up a table comparing (in three columns) the characteristic features of the s-block metals (use group 1 as typical) and the d-block transition metals. 

The. s-block metals are commonly complexed with the macrocyclic cryptands, sepulchrates, and related species to form large, non-interacting cations that are used to stabilize a variety of... 

Hydrides of the s -block metals (excluding Be) can be made by heating the metal with H2. 

In this section, we consider physical properties of the cf-block metals (see cross references in Section 20.1 for further details) an extended discussion of properties of the heavier metals is given in Section 23.1. Nearly all the cf-block metals are hard, ductile and malleable, with high electrical and thermal conductivities. With the exceptions of Mn, Zn, Cd and Hg, at room temperature, the metals possess one of the typical metal structures (see Table 6.2). The metalhc radii (r ,etai) for 12-coordination (Table 6.2 and Figure 20.1) are much smaller that those of the s-block metals of comparable atomic number. Figure 20.1 also illustrates that values of r etaf... 

By donating single electrons, the s-block metals promote a variety of radical reactions, including a number of reductive coupling reactions. 

The s-block metals are among the strongest reductants known and reduce most materials capable of reduction. The reaction with water is shown below for a generic alkali metal (M) ... 

We have emphasized the s-block metals overriding tendency to lose their valence electrons. When the energetics is right, however, alkali metals can also accept an electron to yield alkalide anions, M , with two electrons in the valence s orbitals. Once again, a cryptand does the trick ... 

The first group is the s-block metal alkoxides. There are a few reports on application of them in the catalytic reactions. Zhao et al. have examined stereoselective addition of quinazolines, 77, to terminal alkynes, 78, under mild conditions catalyzed by KO Bu (reaction 7.10) [58]. Bunlaksananusorn and co-workers also used KO Bu for the addition (reaction 7.11) of ketones, 80, and nitriles, 81, to vinylic silanes, phosphines and thio derivatives, 82, within 60-90% yield efficiently [59]. 

Describe some differences between the s-block metals and the d-block metals. 

The s-block metal that lies immediately before the first row of d-block elements in the Periodic Table is calcium (Ca), in Group 2. When we compare the properties of calcium with the first row of transition elements we find some differences despite the fact that they are all metals. You need to know the following comparisons ... 

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