Vertical trends

Figure 3.26 shows that the 7t-electronegativity exhibits horizontal and vertical trends similar to those for a-electronegativity. However, the range of xA(7I) values is seen to be significantly smaller than that of xA(a) values, corresponding to the fact that 7TAb bonds are usually less polarized than periodic variations in pi-bond polarity correspond to rather dramatic variations in the relative lobe sizes of 7t and 7t orbitals cf., for example, the 7tc Ge antibond of Fig. 3.25(a) with the 7tc—o antibond... 

The general procedure for constructing Lewis-like diagrams for transition-metal species can best be illustrated by representative examples. From Table 4.1 one can recognize that the first transition series (Sc-Zn) includes a disproportionate number of exceptional cases compared with later series, and illustrative examples will therefore be drawn primarily from the third transition series (La-Hg). (The somewhat anomalous behavior of the first transition series and general vertical trends in the d-block elements will be discussed in Section 4.10.)... 

Figure 4.93 illustrates some aspects of the break in the vertical trend of atomic orbital energies es and for early, middle, and late transition elements, showing the contrasting behavior of third-series versus first- and second-series elements. The... 

Figure 4.95 Vertical trends in geometry of saturated MH hydrides of group 4 (Ti,...

The most striking vertical trend concerns the metal-hydride bond strengths, as summarized in Table 4.55. We define the first M—H bond strength (A mh(1)) for each species as the energy needed to break the first M—H bond ... 

The vertical trend in d-block bond energies can be rationalized in terms of the relative sizes of s and d valence orbitals. As shown in Fig. 4.94, the d orbitals typically are contracted to lie inside the valence s orbital, but this disparity diminishes on going down a column as the d orbitals grow in size. This growth is physically... 

The proportion of long-chain LAS homologues is greater in the solid phase (solids in suspension and sediment) than in water and greater than in commercial LAS. For LAS clear vertical trends in distribution can be observed both in the water and sediment columns, with relatively enriched concentrations in the surface microlayer and sediment top layers. 

The meteorite data (Fig. 10) are not related by simple mass fractionation. They exhibit a clear negative trend in A Mg -6 Mg space that can be explained by a combination of the presence of excess Mg due to decay of short-lived and extinct A1 and a mass-fractionation component (cf, Fig. 4). This is most easily seen on a plot of A Mg vs. 5 Mg where decay of Al in the absence of fractionation would result in a vertical trend (Fig. 11). The trend is dominated by the Allende chondrules with negative A Mg in the data set but there are hints (e.g., the Bjurbole chondrules) that the trend may extend to positive A Mg as well. Apositive A Mg may signify that bulk Earth has more radiogenic Mg than these primitive samples. Alternatively, it may mean that there are small anomalies in the Mg isotopic system (e.g., excesses in Mg) at the 0.03%o level. 

Figure 11. A Mg vs. 5 Mg plot similar to Figure 10. In this diagram addition of 5 Mg by Al (3+ decay results in a vertical trend. The trend of the data shows that they can only be explained by a combination of mass-dependent fractionation and addition of Mg. The regularity of the trend among different chondritic components argues for a mixing line.

The saturation state of seawater can be used to predict whether detrital calcite and aragonite are thermodynamically favored to survive the trip to the seafloor and accumulate in surfece sediments. Any PIC or sedimentary calcium carbonate exposed to undersaturated waters should spontaneously dissolve. Conversely, PIC and sedimentary calcium carbonate in contact with saturated or supersaturated waters will not spontaneously dissolve. Typical vertical trends in the degree of saturation of seawater with respect to calcite and aragonite are shown in Figure 15.11 for two sites, one... 

The vertical trends in POM fluxes exhibit temporal and geographic variability. This was shown in Figure 23.3, in which seasonal shifts in surface productivity were seen to affect the subsurface particle fluxes even in deep waters. Other processes that can affect the sinking flux of POM include (1) in situ production by mid-water microbes or zooplankton and (2) lateral transport of POM via advective currents. Both can produce mid-water maxima in the sinking organic matter fluxes. Geographic variability in these fluxes is common. As illustrated in Figure 23.6 for the central equatorial Pacific Ocean,... 

In the 5-5 diagrams, plotted with a mineral which exchanges oxygen relatively slowly (quartz) on the horizontal axis and a mineral which exchanges oxygen relatively rapidly (feldspar, biotite) on the vertical axis, the data from the pink pegmatites shows vertical trends which is usually caused by open-system hydro-... 

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