First-row d-block elements

The first row of the d-block contains ten elements, scandium to zinc, in which the 3d sub-level is being filled with electrons. It is these electrons that are responsible for their characteristic properties. 

Nine of these elements are classified as transition elements, but the last member of the row, zinc, does not fully share the properties of the other nine and is not classified as a transition element. 

Zinc does not share these properties it has a relatively low melting point, boiling point and density compared to the transition metals. Zinc has only one stable oxidation state +2. 

The zinc ion is colourless. Zinc shows some catalytic properties and does form complex ions, although this property is not unique to transition metals. Scandium shows some similarities to zinc but is classified as a transition element because it can exist in multiple oxidation states +3 (common), +2 (rare) and +1 (rare). 

There are some vertical chemical similarities between the elements to justify the numbering of the groups within the d-block in the periodic table. For example, in group 3, scandium, yttrium and lutetium all have a common oxidation state of +3. In most cases the three elements in each vertical column have the same outer electron configuration, for example, scandium 3dHs, yttrium 4d 5s and lutetium 5s 6s.  

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Metal-centred (MC) transitions or d-d transitions between the nonbonding and antibonding metal-centred MOs. Such transitions are commonly found among the first-row d-block elements. 

Explain the appearance of the plots of first, second and third ionization enthalpies for the first-row d-block elements as shown in Figure 2.3. 

Metal derivatives of the bis(trimethylsilyl)amido ligand, [(Me3Si)2N], have been extensively investigated for the p- and first-row d-block elements. An exhaustive review by Harris and Lappert, concentrating upon synthetic chemistry, has recently appeared (1). A review of the molecular and electronic structure of three-coordinate and related (Me3Si)2N derivatives, which reports a number of unpublished results has appeared (2). 

Figure 21.33 shows a plot of experimental lattice energy data for metal(II) chlorides of first row d-block elements. In each salt, the metal ion is high-spin and lies in an octahedral environment in the solid state. The double hump in Figure 21.33 is reminiscent of that in Figure 21.32, albeit with respect to a reference line which shows a general increase in lattice energy as the period is crossed. Similar plots can be obtained for species such as MF2, MFj and [MFg] ", but for each series, only limited data are available and complete trends cannot be studied. 

Write out, in sequence, the first row d-block elements and give the valence electronic configuration of each metal and of its ion. 

Data are given for the s-, p- and first row d-block elements. The ionic radius varies with the charge and coordination number of the ion a coordination number of 6 refers to octahedral coordination, and of 4 refers to tetrahedral unless otherwise specified. Data for the heavier block metals and the lanthanoids and actinoids are listed in Tables 22.1 and 27.1. 

The standard electrode potentials, E, for such reduction reactions are related to the free energy change for the process by equation 5.3. Since some elements may exist in a number of different oxidation states, it is possible to construct electrode potential diagrams, sometimes called Latimer diagrams, relating the various oxidation states by their redox potentials. Examples are shown in Figure 5.6 for aqueous solutions of some first-row d-block metals and for some actinides in 1 mol dm acid. In cases where the reduction involves oxide or hydroxide ions bound to... 

Table 4.1 Variation of ion size and average bond distances found for first-row d-block metal ions in common oxidation states and with six-coordinate octahedral geometry. Entries for a second and third row element, to exemplify differences down a column of the Periodic Table d block, appear in italics.

The sterically demanding ligand N(SiMc3)2 has allowed the electronic and EPR spectra of the first row rf-block elements in a purely trigonal planar environment to be measiu d." " All of the data obtained by Bradley et al. on this series were consistent with the theoretical predictions for this geometry, and allowed in some cases values for spin-orbit coupling constants to be evaluated. 

In 1937 English chemist Nevil V. Sidgwick suggested a rule (the octet rule for first-row p-block elements) for complex formation tmder which a metal can acquire ligands until the total number of electrons around it is equal to the number surrounding the next noble gas. This rule was later expanded as the eighteen-electron rule under which a d-block transition metal atom has eighteen electrons in its nine valence orbitals [five n d one (n -I-... 

Although the physical properties of the d-block elements are similar, the chemical properties of these elements are so diverse that it is impossible to summarize them fully. We can, however, observe some of the major trends in properties within the d block by considering the properties of certain representative elements, particularly those in the first row of the block. 

Most d-block elements have more than one common oxidation state (Fig. 16.7). The distribution of oxidation states looks daunting at first sight, but there is a pattern. Except for mercury, the elements at the ends of each row of the d block occur in only one oxidation state other than 0. Scandium, for example, is found only in oxidation state +3, and zinc only as +2. All the other elements of each row have at least two oxidation states. Copper, for example, is found in two oxidation states, +1 (as in CuCl) and +2 (as in CuCl2). Elements close to the center of each row have the widest range of oxidation states. Manganese, at the center of its row, has seven oxidation states. Elements in the second and third rows of the block are more likely to reach higher oxidation states than those in the first row. 

FIGURE 30 A medium-long form and long form depiction of the 14CeTh periodic table. In this representation, the f-block consists of 14 groups of f-elements with cerium (Ce) and thorium (Th) as the first representatives of each row and lutetium (Lu) and lawrencium (Lr) as the last ones. Lanthanum (La) and actinium (Ac) are accommodated as d-block elements in group 3 (NIB) of the periodic table, below scandium (Sc) and yttrium (Y). The d-block has been torn apart in the long form, due to the insertion of the f-block. 

The d-block transition metals, which form a group of elements ten-wide and four-deep in the Periodic Table associated with filling of the five d orbitals, represent the classical metals of coordination chemistry and the ones on which there is significant and continuing focus. In particular, the lighter and usually more abundant or accessible elements of the first row of the d block are the centre of most attention. Whereas stable oxidation states of p-block elements correspond dominantly to empty or filled valence shells, the d-block elements characteristically exhibit stable oxidation states where the nd shell remains partly filled it is this behaviour that plays an overarching role in the chemical and physical properties of this family of elements, as covered in earlier chapters. 

We shall begin a brief examination of metal complexes in biology with a short overview of metals from the first row of the periodic d block found in biomolecules, and follow this with more detail from selected examples. Although the focus below is on d-block elements,... 

Complexes for most d-block elements have been prepared and a recent review (1) updating that of Reynolds (2), summarises these. Considerations of the hard and soft properties of the donor atoms allow us to predict that, in general, sulfoxides should bind via oxygen to the hard first-row transition metals and via sulfur to soft metals, such as those of Group VIII. Both Steric and electronic effects have been shown to dictate the choice of donor atom and these effects may be summarized -... 

Iron as a transition element Why is iron a transition metal To understand this we need to look at the periodic table of elements, where iron occupies a central position in the first row of d block elements. The properties of these elements are transitional between the metallic behaviour of the s-block elements and the variable valency of the p-block. But the variable valency of the transition metals is entirely different to that of the p-block elements. Whereas the latter have valencies that increase in steps of... 

The values of Vetai listed in Table 6.2 refer to 12-coordinate metal centres since not all metals actually adopt structures with 12-coordinate atoms, some values of r etai h ve been estimated. The need for a consistent set of data is obvious if one is to make meaningful comparisons within a periodic sequence of elements. Values of r ,etai (Table 6.2) increase down each of groups 1, 2, 13 and 14. In each of the triads of the d-block elements, rmetai generally increases on going from the first to second row element, but there is httle change on going from the second to third row metal. This latter observation is due to the presence of a filled Af level, and the so-called lanthanoid contraction (see Sections 23.3 and 25.3). 

Table 13.9 displays the elements of the first row of the d-block elements, giving an example of one coloured simple ion for each, where there is one. 

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 ... 

FIGURE 1.63 The elements in the first row of the d block. Top row magnet is levitated by the superconductor If the assembly were (left to right) scandium, titanium, vanadium, chromium, and turned over, the magnet would hang at about the same distance... 

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