Covalent radius bonding

Electronegativity x is the relative attraction of an atom for the valence electrons in a covalent bond. It is proportional to the effective nuclear charge and inversely proportional to the covalent radius ... 

Element Electronegativity Covalent radius, pm Usual coordination number Bond with hydrogen Bond length, pm Bond energy, kj/mot ... 

The single-bond covalent radius of C can be taken as half the interatomic distance in diamond, i.e. r(C) = 77.2pm. The corresponding values for doubly-bonded and triply-bonded carbon atoms are usually taken to be 66.7 and 60.3 pm respectively though variations occur, depending on details of the bonding and the nature of the attached atom (see also p. 292). Despite these smaller perturbations the underlying trend is clear the covalent radius of the carbon atom becomes smaller the lower the coordination number and the higher the formal bond order. 

Using the carbon atom covalent radius 0.77 A and the covalent radii given in Figure 19-3, predict the C—X bond length in each of the following molecules CF<, CBr4, CI4. Compare your calculated bond lengths with the experimental values C—F in CF4 = 1.32 A, C—Br in CBr = 1.94 A, C—I in CI4 = 2.15 A. 

Predict the molecular structures and bond lengths for SiF4, SiCh, SiBn, and SiL, assuming the covalent radius of silicon is 1.16 A. 

Hall, C. M., 96, 373 Halogens atom models, 98 bond energies, 355 chemistry, 98 color, 352 covalent bonds, 97 covalent radius, 355 electron configuration, 352 ionization energies, 353 oxyacids, 358... 

Each atom makes a characteristic contribution, called its covalent radius, to the length of a bond (Fig. 2.21). A bond length is approximately the sum of the covalent radii of the two atoms (36). The O—H bond length in ethanol, for example, is the sum of the covalent radii of H and O, 37 + 74 pm = 111 pm. We also see from Fig. 2.21 that the covalent radius of an atom taking part in a multiple bond is smaller than that for a single bond of the same atom. 

The covalent radius of an atom is the contribution it makes to the length of a covalent bond covalent radii are added together to estimate the lengths of bonds in molecules. 

The values of f (l) given in the table for electronegative atoms are their normal covalent single-bond radii28 (except for boron, discussed below). The possibility that the radius 0.74 A. of Schomaker and Stevenson29 should be used for nitrogen in the metallic nitrides should be borne in mind. 

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... 

In the course of the work it was found that the value assumed five years ago for the carbon double-bond covalent radius (obtained by linear interpolation between the single-bond and the triple-bond radius) is 0.02 A. too large in consequence of this we have been led to revise the double-bond radii of other atoms also. 

The only structurally characterized In—Sb adduct is (Me3SiCH2)3 In—Sb(Tms)3 19 [38], featuring an In—Sb bond distance of 300.8(1) pm. Due to the lack of other structurally characterized In—Sb adducts, no structural comparisons can be made. The In—Sb bond length found in 19 is supposed to be at the lower end of the In—Sb dative bond range since the covalent radius of In (r ov 143 pm) is about 17 pm larger than those of the lighter elements Al and Ga. Therefore, In—Sb dative bonds are expected to... 

The covalent radii for most of the elements were obtained by taking one-half of the length of a single bond between two identical atoms. For example, the covalent radius of sulfur is obtained from the length of the S—S bond in the S8 molecule ... 

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