Metallic radii for

Figure 3. The lattice parameter for the family of rock-salt structure actinide-antimonide compounds is shown where the line is for the corresponding lanthanide compounds. The metallic radii for the light actinide elements are plotted. The smooth line simply connects Ac to the heavy actinides. In both cases the smooth line represents the ideal tri-valent behavior.

Values of Single-bond Radii and Metallic Radii for Coordination Number 12... 

The curve of single-bond metallic radii for the elements of the first long period has a characteristic appearance (Fig. 3) which must be attributed in the main to variation in the type of bond orbital. The rapid decrease from potassium to chromium results from increase in bond strength due to increasing s-p and d-s—p hybridization. The linear section of the curve from chromium to nickel substantiates the assumption that the same bonding orbitals (hybrids of 2.56 3d orbitals, one 4s orbital, and 2.22 4p orbitals) are effective throughout this series. The increase in radius from nickel to copper is attributed not... 

The radii for the elements of the two short periods are shown in Fig. 2. The metallic radii for the elements sodium to silicon lie on a common smooth curve with the normal covalent radii silicon to chlorine. Also the curve of the metallic... 

Most of the known borides are compounds of the rare-earth metals. In these metals magnetic criteria are used to decide how many electrons from each rare-earth atom contribute to the bonding (usually three), and this metallic valence is also reflected in the value of the metallic radius, r, (metallic radii for 12 coordination). Similar behavior appears in the borides of the rare-earth metals and r, becomes a useful indicator for the properties and the relative stabilities of these compounds (Fig. 1). The use of r, as a correlation parameter in discussing the higher borides of other metals is consistent with the observed distribution of these compounds among the five structural types pointed out above the borides of the actinides metals, U, Pu and Am lead to complications that require special comment. 

Fig. 11-9.—Metallic radii for the elements oi the first long period and the second long period. Values of octahedral radii and tetrahedral radii are also represented.

Fig. 11-10.—Metallic radii for the elements of the first very long period,...

L. Pauling, A set of effective metallic radii for use in compounds with the /7-wolfram structure. Acta Cryst. 10, 374-375 (1957). 

Figure 7.6 Metallic radii for coordination number 12, [CN12], Data from Teatum, Gschneidner and Waber, cited by W. Pearson, The Crystal Chemistry and Physics of Metals and Alloys, Wiley-Interscience, New York, 1971, pl51...

Table 3 Predicted metallic radii for the elements Ra to Es, for different...

This is all true when the stoichiometric disulfides are considered. What happens to chemical bonding upon sulfiir loss remains unknown. A possible solution of the problem appeared when the structures of SmSi.90 (Podberezskaya et al. 1999, Tamazyan et al. 2000b), DySi.84 (Podberezskaya et al. 1998), and DyS 7 (Tamazyan et al. 1994) were resolved. Formally, the chemical bonding may be characterized by the ionic formulas and by the interatomic distances in the structural series of the RS2 RS1.90 RSi.g4 RS].76 compounds. These distances are compared with the known radii (metallic, ionic, covalent) taken firom the Table of ionic radii in the ICSD databank (CRISTIN 1986). Considering the structures as alternating square nets, -(S2)-R-S-S-R-(S2-, two types of distances, within each layer (-(S2)-(S2)- R-R S-S ) and between the layers (R-S S-(S2) S-S), have been analyzed. In the sheet (R-S-S-R) or (RS)+ all the R-R and S-S distances are close to the sum of the appropriate metallic radii for R and ionic radii for and the R-S distances are close to the smn of the ionic radii of these elements. This means that the chemical bonding in this sheet is preferably ionic. 

Fig. 7.9 Formation region of various types of Zintl phases of disilicides in a plot of V/n (the cubic root of the cell volume per unit formula MSi2) versus the metallic radii for 12 coordination [21]...

Fig. 2.6. The metallic radii for CN of 12 vs. the atomic number for Ba, the lanthanides and Hf metals, -y refers to -y-Ce, the fee room temperature form and a refers to o-Ce, the collapsed fee low temperature or high pressure form (see eh. 4 sections 2.1 and 2.2). The radius of hypothetical Ce is taken from Gschneidner and Smoluchowski (l%3).

Table 2 summarizes the metal nitrogen bond distances in structurally characterized transition metal-NPR3 coitplexes in vhich a triple metal-nitrogen bond would not force a violation of the 18 electron rule. The differences between M-N distances and metallic radii for these complexes are tend to be somewhat larger than 0.41 A expected for a triple bond. ... 

In this section, we consider physical properties of the d-block metals (see cross-references in Section 19.1 for further details). An extended discussion of properties of the heavier metals is given in Section 22.1. Nearly aU the fi -block metals are hard, ductile and malleable, with high electrical and thermal conductivities. With the exceptions of Mn, Zn, Cd and Hg, at room temperature, the metals possess one of the typical metal structures (see Table 6.2). The metallic radii for 12-coordination (Table 6.2 and... 

The crystal structures, lattice parameters, metallic radii for a coordination number of 12, atomic volumes and the densities of the rare earth metals at 24°C or below are... 

The values plotted are metallic radii for metals and covalent radii for nonmetals. Data for the noble gases are not included because of the difficulty of measuring covalent radii for these elements (only Kr and Xe compounds are known). The explanations usually given for the several small peaks in the middle of some periods are beyond the scope of this discussion. 

The values given, in picometers (pm), are metallic radii for metals, single covalent radii for nonmetals, and ionic radii for the ions indicated. Gold spheres represent neutral atoms blue spheres represent cations and green spheres represent anions. 

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