Ionic radii of elements

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

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... 

When anions are formed, atoms lose electrons. Therefore, the ionic radii of elements are smaller than the corresponding atomic radii. Both ionic and atomic radii of elements in the same period decrease with increasing atomic number. See Figure 13.9. 

Table 1.1. Ionic radii of elements commonly found in clay fractions of soils...

Table 2.5 The ionic radii of elements the most frequently encountered in cement chemistry...

Table 40.1 Ionic radii of elements in the earth s crust coordination number CN is 4. For Ca CN is 6.

Chang, Z., Li., J., Dong, C. Ionization potentials, electron affinities, resonance excitation energies, oscillator strengths, and ionic radii of element Uus (Z = 117) and astatine. J. Phys. Chem. A 114, 13388-13394 (2010)... 

Table 9. Ionic Radii of Actinide and Lanthanide Elements...

In the geochemistry of fluorine, the close match in the ionic radii of fluoride (0.136 nm), hydroxide (0.140 nm), and oxide ion (0.140 nm) allows a sequential replacement of oxygen by fluorine in a wide variety of minerals. This accounts for the wide dissemination of the element in nature. The ready formation of volatile silicon tetrafluoride, the pyrohydrolysis of fluorides to hydrogen fluoride, and the low solubility of calcium fluoride and of calcium fluorophosphates, have provided a geochemical cycle in which fluorine may be stripped from solution by limestone and by apatite to form the deposits of fluorspar and of phosphate rock (fluoroapatite [1306-01 -0]) approximately CaF2 3Ca2(P0 2 which ate the world s main resources of fluorine (1). 

Chapter 30). Similar plots are obtained for the atomic and ionic radii of the elements and an inverted diagram is obtained, as expected, for the densities of the elements in the solid state (Fig. 2.2). 

The effect of the lanthanide contraction on the metal and ionic radii of hafnium has already been mentioned. That these radii are virtually identical for zirconium and hafnium has the result that the ratio of their densities, like that of their atomic weights, is very close to Zr Hf = 1 2.0. Indeed, the densities, the transition temperatures and the neutron-absorbing abilities are the only common properties of these two elements which differ... 

Atomic and ionic radii of the main-group elements. Negative ions are always larger than atoms of the same element, whereas positive ions are always smaller than atoms of the same element. ... 

The crystal structures of Hf 2 (OH) 2 (S0O 3 (H2O) i, (14) and Ce2(0H)2(S0i,)3 (H20)it (14) also have been determined and found to be isomorphous to the zirconium compound. The cell constants for this series of four isomorphous compounds reflect the effect of the ionic radii on the dimensions of the unit cell. The values for these cell constants are in Table II. Thus, the cell constants for the zirconium and hafnium compounds are nearly identical and smaller than the cell constants for the cerium and plutonium compounds which are also nearly identical. This trend is exactly that followed by the ionic radii of these elements. 

HCURE 15.10 The atomic and ionic radii of the Group 16/VI elements increase steadily down the group. The values shown are in picometers, and each anion (shown green) is substantially larger than its neutral parent atom. 

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.

Table 2. Ionic radii of U-series elements and their proxies...

Ionic radii of the elements of the first transition metal period in octahedral coordination... 

The ionic radii of ionized main-group elements (in pm). Cations have smaller radii and anions larger radii than their corresponding atoms. 

The XRD analyses revealed presence of AEO and Nd203, SrC03 (about 62 wt%) in SrNd-SG sample, CaC03 and Ca(OH)2 (about 5 wt%) in CaNd-SG. Solid solutions of Nd in AEO and of AEE in Nd203 were observed in all samples. The calculation of lattice constants and unit cell volumes (UCV) showed modification of the oxide lattice by foreign cations. The formation of solid solutions obviously depended of the relative ionic radii of the elements equal to 0.0995 nm for Nd3+, 0.072 for Mg2+, 0.1 for Ca2+,... 

It is interesting to note that direct synthesis gives bis(phthalocyanine) complexes oftrivalent metals as anionic species, which are gradually transformed into neutral paramagnetic species under exposure to air. The stability of the anionic species decreases in the series oflanthanide complexes with a decrease in the ionic radii of the elements [135]. 

Figure 10.6 Onuma diagrams for crystal/melt trace element distributions. Ionic radii of Whittaker and Muntus (1970). (A) Augite/matrix distribution, data of Onuma et al.

Ahrens L. H. (1952). The use of ionization potentials, 1 Ionic radii of the elements. Geochim. Cosmochim. Acta, 2 155-169. 

Besides luminescence properties, we also added the short data on color of corresponding minerals, because, as was already mentioned, such information is often useful for an imderstanding of liuninescence nature. The data on ionic radii of different elements and the main structural data are taken from corresponding Internet sites. 

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