5d transition series

The lanthanide contraction has a knock-on effect in the elements in the 5d transition series. It would naturally be expected that the 5d elements would show a similar increase in size over the 4d transition elements to that which the 4d elements demonstrate over the 3d metals. However, it transpires that the lanthanide contraction cancels this out, almost exactly, and this has pronounced effects on the chemistry, e.g. Pd resembling Pt rather than Ni, Hf is extremely similar to Zr. 

Hafnium, element 72, is found in Period 6, as shown in Fig. 12.31. Note that it occurs just after the lanthanide series. Thus the 4f orbitals are already filled. Hafnium is the second member of the 5d transition series and has two 5d electrons. The configuration is... 

In comparing the 3d, 4d, and 5d transition series, it is instructive to consider the atomic radii of these elements (Fig. 20.3). Note that there is a general,... 

Stable binary metal carbonyls, negatively charged or uncharged, exist for all the elements of the 3d, 4d, and 5d transition series from CSroup 4 to Group 10, with the exception of palladium. As shown in Table 1, some of the elements (Ti, Zr, Hf, Nb, Ta, and Pt) have anionic carbonylmetalates only and no stable uncharged derivatives have so far been reported. Of the known metal carbonyls, only those of Group 6, Group 7 (with the exclusion of technetium), iron, ruthenium, cobalt and nickel have been used much in catalytic processes. 

Periods 4, 5, 6, and 7 incorporate the c/-block transition elements. The general pattern, as you ve seen, is that the (ii — )< / orbitals are filled between the ns and 71/7 orbitals. Thus, Period 5 follows the same general pattern as Period 4. In Period 6, the 65 sublevel is filled in cesium (Cs) and barium (Ba), and then lanthanum (La Z = 57), the first member of the 5d transition series, occurs. At this point, the first series of inner transition elements, those in which / orbitals are being filled, intervenes (Figure 8.6). The / orbitals have / = 3, so the possible m values are —3, —2, —1, 0, +1, +2, and -f3 that is, there are seven/orbitals, for a total of 14 elements in each of the two inner transition series. 

Thus the 4f orbitals are already filled. Hafnium is the second member of the 5d transition series and has two 5d electrons. Its electron configuration is... 

Stability of the metal-carbon monoidde bond. A low formal oxidation state, substitution of carbonyl groups by other ligands, and a hexacoordinate central metal atom of either the 3d or the 5d transition series favor a more stable metal-carbon monoxide bond. 

The transition elements occupy groups 3-11 of the periodic table and are characterized electronically as having a partially filled d subshell. A related but not equivalent term is rf-block element, which includes all of these plus the elements in group 12. The first sequence of tf-block elements begins in the fourth period with scandium which has one M electron and continues through zinc, which has ten. The second (Ad) and third (5d) transition series are analogous. 

The number of bonding electrons at the beginning of the 5d series may be inferred from comparing the measured atomic volumes of rare earths and transition metals. On the right in fig. 1, Yb is clearly a divalent lanthanide and, therefore, has two valence electrons. Similarly, lutetium is a trivalent lanthanide and has three valence electrons. On the left in the same figure, these two elements are seen to be also the first two members of the 5d transition series and the third, hafnium, will have four valence electrons. 

Fig. 2. Ratio of the equilibrium atomic volumes of the Z and Z + 1 elements for the lighter 3d, 4d and 5d transition series.

Lanthanum (Z = 57), with the electron configuration xenon core (4/ 5d 6s ), is the first element in the 5d transition series and the rare earths, which begins with Ce(Z = 58), are often referred to as the... 

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