Alkaline earth metals ionic size

The superoxides are ionic soHds containing the superoxide, O - A comprehensive review of the superoxides was pubHshed ia 1963 (109) they are described ia Reference 1. Superoxides of all of the alkaU metals have been prepared. Alkaline-earth metals, cadmium, and 2iac all form superoxides, but these have been observed only ia mixtures with the corresponding peroxides (110). The tendency to form superoxides ia the alkaU metal series iacreases with increasing size of the metal ion. 

Based on the concept of mixed-framework lattices, we have reported a novel class of hybrid solids that were discovered via salt-inclusion synthesis [4—7]. These new compounds exhibit composite frameworks of covalent and ionic lattices made of transition-metal oxides and alkali and alkaline-earth metal halides, respectively [4]. It has been demonstrated that the covalent frameworks can be tailored by changing the size and concentration of the incorporated salt. The interaction at the interface of these two chemically dissimilar lattices varies depending upon the relative strength of covalent vs. ionic interaction of the corresponding components. In some cases, the weak interaction facilitates an easy... 

In many of its features, the chemistry of manganese(II) spans that of the alkaline earth metals (especially magnesium(II) and that of the later first row transition metals. There are also parallels with cadmium(II) rather than zinc(II). These are all related to the more significantly ionic bonding for manganese and to the size of the metal ion . 

Table 2 presents effective ionic radii for many metal ions. For any metal ion, the radius increases with coordination number since the greater number of bonds weakens the strength of any one bond. The radius of the most common coordination number is underlined in Table 2. The alkali and alkaline earth metal ions exhibit variable coordination numbers without strong directionality in bonding. Because they are of similar size, Ca + and Na+ of differing charges...

The second class of alkaline earth metals involves the heavier congeners, although radium, as a radioactive element, is not studied in detail. The significant increase in ionic size and reduction in electronegativity experienced by these metals (Ca (CN 6) 1.14 A, EN = 1.04 Sr (CN 6) 1.27 A, EN = 0.97 ... 

MC) [2,43 5] should lead to novel supramolecular architectures of well-defined host-guest compounds. Since the ionic radii of alkaline and alkaline earth metal cations differ significantly in size, whereas the diameter of a given metallacrown essentially does not change, the inclusion of small cations such as Na+ or Ca + should yield a metallacoronate [19,45-47] with 1 1 stoichiometry (M+ MC =... 

Some ceramics having large values of Eg are listed in Table 30.3. No entirely satisfactory relationship has been established between the ionic character of the bond and the atom size on Eg. In a homologous series of oxides, such as the oxides of the alkaline-earth metals. Eg increases with increasing ionic potential, < ), of the cation as shown in Figure 30.24. 

Cheng and co-workers recently reported Fc-cyclopeptides 12-15 (Scheme 5.4) and showed that they acted as redox-switchable cation receptors [26]. These Fc-cyclopeptides exhibited strong anodic shifts of their electrode potentials in the presence of alkaline earth metals and lanthanides. The extent of the anodic shift can be correlated with the charge density of the metal ion with a bias toward binding of lanthanides, alkaline earth metals, and the least sensitivity to alkaline metals [26]. Chowdhury et al, reported the syntheis and interaction of cychc Fc-Histidine conjagates 16 with metal ions (Scheme 5.5). Electrochemical measurements showed that the compound exhibited cathodic shifts in the order Na Li K+>Cs which in the order of their ionic sizes and suggest that the observed shift relates to the cavity of the compound [27]. 

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