Single bonds, formulation

Fig. 13 is a drawing of electron-domain models of some Group VI hexafluorides. Open circles represent the electron-pairs of four of the six bonds to fluorine atoms in a Lewis, single-bond formulation of these molecules. Solid circles represent the atomic cores of oxygen, sulfur, selenium, tellurium, tungsten, and uranium (core radii, in hundreths of A, 9, 29, 42, 56, 62, and 80 2>, respectively). These hexafluorides are, in order, non-existent, extra-ordinarily unreactive, hydrolyzed slowly, hydrolyzed completely at room temperature in 24 hours, hydrolyzed readily, and hydrolyzed very rapidly. 

NH2OH can exist as 2 configurational isomers (cis and trans) and in numerous intermediate gauche conformations as shown in Fig. 11.7. In the crystalline form, H bonding appears to favour packing in the trans conformation. The N-O distance is 147 pm consistent with its formulation as a single bond. Above room temperature the compound decomposes (sometimes explosively) by internal oxidation-reduction reactions into a complex mixture of N2, NH3, N2O and H2O. Aqueous solutions are much more stable, particularly acid solutions in which the compound... 

In the following discussion use is made of an equation that has been formulated by the method given earlier in a discussion of the equation for resonance between a single bond and a double bond11 and of the interatomic distances in the carbon monoxide molecule and carbon dioxide molecule.13 The potential function for the bond is assumed to have the form... 

An equation has been formulated to express the change in covalent radius (metallic radius) of an atom with change in bond number (or in coordination number, if the valence remains constant), the stabilizing (bond-shortening) effect of the resonance of shared-electron-pair bonds among alternative positions being also taken into consideration. This equation has been applied to the empirical interatomic-distance data for the elementary metals to obtain a nearly complete set of single-bond radii. These radii have been compared with the normal covalent... 

The determination of values of interatomic distances in molecules has been found to provide much information regarding electronic structure, especially in the case of substances which resonate among two or more valence-bond structures. The interpretation of interatomic distances in terms of the types of bonds involved is made with use of an empirical function formulated originally for single bond-double bond resonance of the carbon-carbon bond.1 There are given in this... 

The four-membered ring of 66 [Li (dme)3] was perfectly planar with two pairs of distinctly different skeletal Ge-Ge bonds of 2.5116(6) and 2.3679(6) A the former is typical for the Ge-Ge single bonds, whereas the latter is close to the valnes of Ge=Ge double bonds. Such crystallographic features led to the formulation of the allylic-type strncture of 66 , in which the negative charge is delocalized over the Gej fragment of the four-membered ring. 

It will be shown in the following section that the postulate of additivity is valid for a large number of single bonds and that the values of A can be used as the basis for the formulation of an extensive scale of electronegativities of the elements. In a few cases, however, the postulate of additivity is found not to hold. The following section is devoted to a discussion of these cases. 

The first values of covalent radii, as given in Table 7-2, were formulated before experimental values were available for F—F, O—O, and N—N single bonds. An electron-diffraction study of F2 by Brockway9 then gave the F—F distance as 1.45 A (a value substantiated by Rogers, Schomaker, and Stevenson, Table 7-3, who found 1.435 0.010 A), whereas the accepted radius of fluorine would require 1.28 A. Similar discrepancies were then reported for O—O, for which... 

The equation wras formulated in the following way. In Section 7-6 it was pointed out that the dependence of bond length on bond order n9 over the range n9 = 1, 2, 3 is D(n9) D(l) — 0.71 log n. This equation might be used also for values of nf less than 1 for example, for a bond with bond order it makes the bond length 0.21 A greater than it is for a single bond. 

A set of empirical equations representing the single-bond radius of a transition element as a function of atomic number and degree of hybridization of the bond orbitals has been formulated.28 These... 

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