Periodic trends ionic radii

The radii of cations and anions derived from atoms of the main-group elements are shown at the bottom of Figure 6.13. The trends referred to previously for atomic radii are dearly visible with ionic radius as well. Notice, for example, that ionic radius increases moving down a group in the periodic table. Moreover the radii of both cations (left) and anions (right) decrease from left to right across a period. 

Atomic radii typically decrease from left to right across a period and increase down a group (Fig. 14.2 see also Fig. 1.46). As the nuclear charge experienced by the valence electrons increases across a period, the electrons are pulled closer to the nucleus, so decreasing the atomic radius. Down a group the valence electrons are farther and farther from the nucleus, which increases the atomic radius. Ionic radii follow similar periodic trends (see Fig. 1.48). 

Use the Interactive Periodic Table (eChapter 5.1) to compare the atomic radius and the ionic radius of the elements in group 2A. How does the ionic radius compare to the atomic radius Explain this trend. 

Rates for d2 -d6 complexes show no trend with ionic radius, however, on descending a column in the periodic table the rates always decrease Fe(III) > Ru(III) and Co(III) > Rh(IlI). 

One property of a transition metal ion that is particularly sensitive to crystal field interactions is the ionic radius and its influence on interatomic distances in a crystal structure. Within a row of elements in the periodic table in which cations possess completely filled or efficiently screened inner orbitals, there should be a decrease of interatomic distances with increasing atomic number for cations possessing the same valence. The ionic radii of trivalent cations of the lanthanide series for example, plotted in fig. 6.1, show a relatively smooth contraction from lanthanum to lutecium. Such a trend is determined by the... 

Because of the arrangement of elements on the periodic table, there are several patterns that can be seen between the elements. These patterns, or periodic trends, can be observed for atomic radius, ionic radii, ionization energies, electron affinities, and electronegativities. You should be familiar with the periodic and group trends for each of these. 

A The general trend to more exothermic values with increasing atomic number is attributable to the decrease in ionic radius across the period because, as the anion-cation separation becomes smaller, the lattice enthalpy increases (equation 3.3). Superimposed on this trend is the effect of CFSE values. These are small in comparison to the overall magnitude of A// , but nonetheless have a significant effect. The double dip in the plot may be accounted for in terms of the variation in high-spin CFSE values across the first-row d-block. as shown in Figure 6.3. This shows respective CFSE contributions to of -(YsfA j for Ti-", -(V Aq for... 

Complete the concept map using the following terms electronegativity, electron configuration, periodic trends, ionic radius, atomic radius, ionization energy, and periodic table. 

Figure 8.9 shows the radii of ions derived from the familiar elements, arranged according to elements positions in the periodic table. We can see parallel trends between atomic radii and ionic radii. For example, from top to bottom both the atomic radius and the ionic radius increase within a group. For ions derived from elements in different groups, a size comparison is meaningful only if the ions are isoelectronic. If we examine isoelectronic ions, we find that cations are smaller than anions. For example, Na is smaller than F . Both ions have the same number of electrons, but Na... 

STEP 3 Unfold the sheet and draw lines along all fold lines. Label as follows Periodic Trends, Periods, and Groups in the first row, and Atomic Radius, Ionic Radius, Ionization Energy, and Electronegativity in the first column. 

Also, the ionic radii change with the oxidation state of the ion, with the increase of the oxidation state leading to a decrease in ionic radius. Figures 2.8,2.9, and 2.10 compare the atomic radius, ionic radius, and the covalent radius for periods 1 and 2, and period 3 and period 4 elements, respectively (Brezeanu et al. 1990 Whitten et al. 1988 Housecroft and Constable 1997). It can be seen from these figures that covalent radii follow the same general trend as the ionic radii they have even smaller values than the ionic radii for metals and higher values for the nonmetals. 

Using periodic trends to obtain relative ionic radii Given a series of ions, arrange them in order of increasing ionic radius. (EXAMPLE 9.4)... 

The groups and periods of the periodic table display general trends in the following properties of the elements electron affinity, electronegativity, ionization energy, atomic radius, and ionic radius. 

Lattice energy depends on the magnitudes of the charges and on the distance between them. For example, Lil, Nal, and KI all have the same anion (I ) and all have cations with the same charge (+1). The trend in their lattice energies (Lil > Nal > KI) can be explained on the basis of ionic radius. The radii of alkali metal ions increase as we move down a group in the periodic table ( LI < Na-r < k-h) [ W Section 7.6]. Knowing the radius of each ion, we can use Coulomb s law to compare the attractive forces between the ions in these three compounds ... 

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