Ionic effective radius

Table 4.6 Atom Radii and Effective Ionic Radii of Elements...

Element Atom radius, pm Effective ionic radii, pm ... 

Shannon and Prewitt base their effective ionic radii on the assumption that the ionic radius of (CN 6) is 140 pm and that of (CN 6) is 133 pm. Also taken into consideration is the coordination number (CN) and electronic spin state (HS and LS, high spin and low spin) of first-row transition metal ions. These radii are empirical and include effects of covalence in specific metal-oxygen or metal-fiuorine bonds. Older crystal ionic radii were based on the radius of (CN 6) equal to 119 pm these radii are 14-18 percent larger than the effective ionic radii. 

Table 8.2 Approximate Effective Ionic Radii in Aqueous Solutions at 25°C 8.4...

Values for the activity coefficients of ions in water at 25°C are given in Table 8.1 in terms of their effective ionic radii. 

In Section 4 the data on bond lengths and strengths have been vastly increased so as to include not only the atomic and effective ionic radii of elements and the covalent radii for atoms, but also the bond lengths between carbon and other elements and between elements other than carbon. All... 

Figure 3A Plot of effective ionic radii versus oxidation state for various elements.

Effective Ionic Radii In pm for Various Oxidatiop States (In parentheses)... 

The uncertainty of the proper coordination number of any particular plutonium species in solution leads to a corresponding uncertainty in the correct cationic radius. Shannon has evaluated much of the available data and obtained sets of "effective ionic radii" for metal ions in different oxidation states and coordination numbers (6). Unfortunately, the data for plutonium is quite sparse. By using Shannon s radii for other actinides (e.g., Th(iv), U(Vl)) and for Ln(III) ions, the values listed in Table I have been obtained for plutonium. These radii are estimated to have an uncertainty of 0.02 X ... 

Estimated Effective Ionic Radii for Plutonium Coordination... 

Figure 7-2. Effective ionic radii of high- and low-spin divalent and trivalent ions of the first row transition elements. The filled points represent high-spin ions.

R. D. Shannon, Revised effective ionic radii and systematic studies of interatomic distances in halides and chalco-... 

The effective ionic radii of Shannon and Prewitt (1969) can frequently be used to predict average interatomic distances and to correlate unit cell volumes of series of isostructural oxides and fluorides. However, some systematic discrepancies were recently found in tetrahedral oxy-anion distances and in the unit cell volumes of certain series of fluoride compounds. It was pointed out by Banks, Greenblatt, and Post (1970) that the observed V—0 distances in Ca2VC>4Cl are smaller than those predicted by the effective ionic radii. Subsequently, the discrepancies in Ca2VC>4Cl and other tetrahedral oxy-anion distances were attributed to covalency effects (Shannon, 1971, and Shannon and Cairo, 1972) in which bonds exhibiting a greater degree of covalency were assumed to shorten. 

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