Pauling atomic radii

Linus Pauling, Atomic Radii and Interatomic Distances in Metals, J. Am. Chem. 

The length of an M-M multiple bond is judged by the formal shortness ratio, or FSR, defined as the M-M distance divided by the sum of the appropriate Pauling atomic radii. [Re2Cl8] has an FSR of 0.87, for... 

Element Atomic number Outer electrons Atomic radius (nm) m.p. (K) h.p. (K) 1st ionisation energy (kj Electro- negativity (Pauling)... 

The critical sizes of the reactant molecules were estimated and are shown in Figure 5, where the figures for 2-hexanol, isopropylacetate, sec-butylacetate and cyclohexylacetate are estimated by MM2 from Pauling s atomic radius and molecular model [18]. Therefore, the unique catalysis of Cs2.2 is understood if one assumes that it is active only for small molecules. In other words, this catalyst exhibits "reactant shape selectivity", where the catalyst differentiates the reactants according to their size. 

The Pauling electronegativities of carbon and tellurium are, respectively, 2.5 and 2.1. This, in addition to the large volume of the tellurium atom (atomic radius 1.37, ionic radius 2.21), promotes easy polarization of Te-C bonds. The ionic character of the bonds increases in the order C(sp ) Te>C(sp ) Te>C(sp)-Te, in accordance with the electronegativity of carbon accompanying the s character (Table 1.1). 

Element Atomic number Atomic mass Electronic configuration Pauling electronegativity Ionization potential Ionic radius Atomic radius... 

The unique ligating behavior of the bridging 2,6-dimethoxyphcnyl ligand with respect to promoting a substantial decrease in the metal atom separation for molybdenum(II) dimers is even more prominent in the case of chromium. The chromium-chromium distance of 1.847(1) A in Cr2(DMP)4 (90) is more than 0.1 A less than the corresponding value in any other chromous dimer yet reported. To compare homonuclear multiple bonds among elements with inherently different atomic radii, Cotton, Koch, and Millar proposed a normalized value for intemuclear distances based on Pauling s atomic radius of the element in question (209). A simple definition of formal shortness as t/(M—M)/2r(M) then follows as a measure of the relative compactness of the attractive interaction (90). The formal shortness ratio of 0.778 for the quadruple bond in... 

Atomic radius (nm) Observations Electronegativity (Pauling) Ionization energy (kJ/mol) Melting point (K)... 

For the relation between the bond order n and the interatomic distance or more specifically the atomic radius Pauling uses the formula rx — rn = 0.300 log n (rx bond radius for a pure single bond). Such an expression is found to be valid for the C—C bond with a coefficient of 0.353. 

Table 3. Atomic radii (in A) of the atoms which form B32 type compounds. rB32 is the half nearest neighbour distance in Zintl phases AB, r o , is the atomic radius according to Goldschmidt (C.N. 8), rjo is the ionic and r ov the covalent radius for tetrahedral coordination (C.N. 4) according to Pauling ...

Examples of valuable static atomic properties are atomic number, atomic mass (AMU), Pauling electronegativity, 1st ionization potential (V) of atom in ground state, atomic radius (pm), covalent radius (pm), and atomic volume (cmYM). 

The solubility of the cations is closely related to their hydration enthalpies. It has been found that it is possible to correlate the hydration enthalpies of cations with the inverse of their effective hydration radii in nm). Thus, by adding 0.085 nm ( radius of the oxygen atom in water) to the Pauling crystal radius, the following expression is obtained ... 

Nickel is found in the rare +1 oxidation state in Rb4[Ni2(CN)J. There are two crystallographically independent [Nij(CN)6] anions which contain planar Ni(CN)a units linked together by a strong Ni-Ni bond, so that the co-ordination at each nickel atom is approximately square-planar. The mean angle between the nickel co-ordination planes is 86°. The two Ni-Ni distances are 2.32 and 2.29 A, not significantly different from twice the Pauling covalent radius of nickel (2.30 A). The mean Ni-C distance is 1.91 A. Two crystal structures containing the tetracyanonickelate anion have been described. - ... 

The 18 selected properties were atomic mass (A), density (d), atomic radius (r), first (II), second (12) and third (13) ionization energy, Pauling electronegativity (X), melting point (MP), boiling point (BP), enthalpy of fusion (HF), vaporization (ITV), atomization (HA), standard entropy (S), specific heat capacity (SHC), surface tension (ST) at the melting point, electrical resistivity (ER), heat conductivity (HC), and the formation free energy of the chloride Ends per mol of Cl (FFE)—as a characteristic of chemical reactivity. 

Since the atomic sizes are different in the substances with different kinds of chemical bond. It is necessary to assign the atoms of elements three kinds of system of atomic radius. In ionic systems, we call the size of ions as ionic radius. In covalent compounds, system of covalent radius is used. And the atomic radius in metallic systems is called metallic radius of elements. In his classical work, Pauling has assigned the values of these three kinds of radius. Pauling s values of atomic or ionic radii have been widely used till now. But there are still other systems proposed by other authors in later years. 

Table 2.2 Electronegativity, possible valences, and the CA -related atomic radius of typical elements (after Goldschmidt [2] and Pauling [1])...

A two-dimensional plot, as we saw in connection with Pearson s work, can be more informative than a one-dimensional one. In Figure 12 the Pauling electronegativity and atomic radius (in a 12-fold-coordinated structure, which is appropriate here) of nontransition... 

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