D-block metals

Many metallic elements in the p and d blocks, have atoms that can lose a variable number of electrons. As we saw in Section 1.19, the inert-pair effect implies that the elements listed in Fig. 1.57 can lose either their valence p-electrons alone or all their valence p- and s-electrons. These elements and the d-block metals can form different compounds, such as tin(II) oxide, SnO, and tin(IV) oxide, Sn02, for tin. The ability of an element to form ions with different charges is called variable valence. 

The product of the second reaction is sodium aluminate, which contains the alumi-nate ion, Al(OH)4. Other main-group elements that form amphoteric oxides are shown in Fig. 10.7. The acidic, amphoteric, or basic character of the oxides of the d-block metals depends on their oxidation state (Fig. 10.8 also see Chapter 16). 

Metals form basic oxides, nonmetals form acidic oxides the elements on a diagonal line from beryllium to polonium and several d-block metals form amphoteric oxides. 

The metallic hydrides are black, powdery, electrically conducting solids formed by heating certain of the d-block metals in hydrogen (Fig. 14.9) ... 

The interstitial carbides are compounds formed by the direct reaction of a d-block metal and carbon at temperatures above 2000°C. In these compounds, the C atoms occupy the gaps between the metal atoms, as do the H atoms in metallic hydrides (see Fig. 14.9). Here, however, the C atoms pin the metal atoms together into a rigid structure, resulting in very hard substances with melting points often well above 3000°C. Tungsten carbide, WC, is used for the cutting surfaces of drills, and iron carbide, FesC, is an important component of steel. 

Cyanides are strong Lewis bases that form a range of complexes with d-block metal ions. They are also famous as poisons. When they are ingested, they combine with certain protein molecules—the cytochromes—involved in the transfer of electrons and the supply of energy in cells, and the victim dies. 

Carbon forms ionic carbides with the metals of Groups 1 and 2, covalent carbides with nonmetals, and interstitial carbides with d-block metals. Silicon compounds are more reactive than carbon compounds. They can act as Lewis acids. 

Hydrogen sulfide dissolves in water to give a solution of hydrosulfuric acid that, as a result of its oxidation by dissolved air, slowly becomes cloudy as S8 molecules form and then coagulate. Hydrosulfuric acid is a weak diprotic acid and the parent acid of the hydrogen sulfides (which contain the HS ion) and the sulfides (which contain the S2 ion). The sulfides of the s-block elements are moderately soluble, whereas the sulfides of the heavy p- and d-block metals are generally very insoluble. 

Why Do We Need to Know This Material The d-block metals are the workhorse elements of the periodic table. Iron and copper helped civilization rise from the Stone Age and are still our most important industrial metals. Other members of the block include the metals of new technologies, such as titanium for the aerospace industry and vanadium for catalysts in the petrochemical industry. The precious metals—silver, platinum, and gold—are prized as much for their appearance, rarity, and durability as for their usefulness. Compounds of d-block metals give color to paint, turn sunlight into electricity, serve as powerful oxidizing agents, and form the basis of some cancer treatments. 

The Industrial Revolution was made possible by iron in the form of steel, an alloy used for construction and transportation. Other d-block metals, both as the elements and in compounds, are transforming our present. Copper, for instance, is an essential component of some superconductors. Vanadium and platinum are used in the development of catalysts to reduce pollution and in the continuing effort to make hydrogen the fuel of our future. 

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 atomic radii of the d-block metals are similar but tend to decrease across a series. The lanthanide contraction accounts for the smaller than expected radii and higher densities of the d-block atoms in Period 6. 

FIGURE 16.3 Because the atomic radii of the c/-block elements are so similar, the atoms of one element can replace the atoms of another element with minor modification of the atomic locations consequently, d-block metals form a wide range of alloys. 

Self-Test 16.1A Predict trends in ionization energies of the d-block metals. 

Self-Test 16.1B Six of the d-block metals in Period 4 form +1 ions. Predict trends in the radii of those ions. 

Like some other d-block metals, such as nickel, iron can form compounds in which its oxidation number is zero. For example, when iron is heated in carbon monoxide, it reacts to form iron pentacarbonyl, Fe(CO)5, a yellow molecular liquid that boils at 103°C. 

Some of the critical enzymes in our cells are metalloproteins, large organic molecules made up of folded polymerized chains of amino acids that also include at least one metal atom. These metalloproteins are intensely studied by biochemists, because they control life and protect against disease. They have also been used to trace evolutionary paths. The d-block metals catalyze redox reactions, form components of membrane, muscle, skin, and bone, catalyze acid-base reactions, control the flow of energy and oxygen, and carry out nitrogen fixation. 

We have already mentioned some of the important roles that the d-block metals play in virtually every aspect of our lives. Steel, an alloy based on iron, is important in construction and transportation and the nonferrous alloys, those based on other metals—most notably, copper—are also important in industry, for their corrosion resistance and strength. Some of these alloys are also desired for their magnetic properties. 

A series of amine-tethered nucleobases such as 8 has also been developed. These ligand systems have allowed the interaction of d-block metal ions with the N3pUrine site to be probed and an indication of base-specific metal-ion binding has begun to emerge (55-58). 

The choice of metal ion in this work is interesting since it has been known for a considerable time that Ag+ is a rare example of a d-block metal ion that does not disrupt the duplex DNA structure (172,173). Rationalization of this effect has tended to focus on the possible base-pair crosslinking due to the preferred linear coordination geometry of Ag1 ions (174). The importance of Ag+ DNA coordination chemistry to the procedure described is not clear. However, reports that other metal ions, e.g., Pdri (175), can be plated to DNA to fabricate metallic wires (Fig. 51) suggests that this may not be essential. 

The metals found in group IA of the periodic table are known as the alkali metals, and those in group IIA are the alkaline earths. Metals found in the groups between IIA and IIIA (the so-called d-block metals) are the transition metals. The series of elements following lanthanum (Z = 57, the/-block metals) 355... 

Compounds with Bonds between Silicon and d-Block Metal Atoms... 

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