Electronegativity and Bond Type: Predicting Bond Type

Abstract

While most general chemistry textbooks recognize that differences in electronegativity between bonded atoms provide only an indication of bond type, the difference function of electronegativity itself is both inadequate and improper for determining bond type. An alternative algorithm based on the unfunctionalized values of electronegativity for the two bonded atoms in binary compounds of representative elements provides much better discrimination between ionic and covalent bonding. This algorithm not only removes the ambiguity introduced by the difference function, but at the same time provides for the natural inclusion of the third type of interatomic bond--metal-metal bonding. Textbook authors should indicate that the absolute values of electronegativity, not their differences, are most useful for predicting bond type. Also, the value of electronegativity of the element of higher electronegativity in binary compounds determines whether the compound will be metallic. If a compound is not metallic, the electronegativity of the element of lower electronegativity determines whether the compound will exhibit primarily ionic or covalent character if that element is representative. If the element of lower electronegativity is a transition metal, the bond character is not predictable using electronegativities alone.

Bonding Energetics in Alkaline Metal Alkoxides and Phenoxides

“…The lattice energies of the alkoxide compounds in Table 3 are rather high, only some 50–100 kJ mol −1 lower than the corresponding hydroxides, suggesting in principle a considerable ionic character for the MOR bonds. The predominantly ionic character of the various alkoxides investigated in this work could also be suggested by the success of Kapustinskii equation in reproducing their enthalpies of formation (Table 2) and by the use of a diagram first proposed by Sproul for solid binary compounds37, 38 (Figure 4). This two‐dimensional graph has been shown to provide suggestive insights into the nature of bonding by separating ionic, metallic, and covalent compounds into three distinctly demarcated areas.…”

“…MOR in the case of the alkaline metal alkoxides or phenoxides). The vertical and horizontal limiting lines correspond to χ hi =2.2 and χ lo =1.7, respectively, as proposed by Sproul 38. The plots for the methoxides, tert ‐butoxides and phenoxides indicated in Figure 4 were based on the following electronegativity data (Pauling's scale):39, 40 χ (Li)=0.97, χ (Na)=0.91, χ (K)=0.73, χ (Rb)=0.69, χ (Cs)=0.62, χ (OCH 3 )=2.52, χ (O‐ t C 4 H 9 )=2.40, and χ (OC 6 H 5 )=2.56.…”

Averaged Scale in Electronegativity Joined to Physicochemical Perturbations. Consequences of Periodicity

“…For this reason, the ratios of electronegativity are lower in the post-transition heavy metals, as seen in Table S6A (allen scale: ratio = low in P4 to P6). Nevertheless, Sproul 34 has found that Allen’s electronegativity scale is one of the more valid scales for analyzing the tripartite separation in 311 ionic, covalent, and metallic compounds, as explained above. Indeed, other scales can give almost the same results for the tripartite separation 34a of type of bonds as it happens with Nagle’s and Batsanov’s electronegativity scales, Batsanov’s scale being the best.…”

“…Also, the lines formed from the electronegativity values of these elements in the van Arkel–Ketelaar’s triangle separate the regions of covalent, metallic, or ionic chemical bonds. We have also considered Sproul’s 34 and Meek’s 35 samples for the analysis of van Arkel–Ketelaar’s triangle in the tripartite separation, which are plotted in Section S-2 of the Supporting Information . The first digit between parenthesis in part (a) of these figures is the number of compounds outside the limits of the type of bond, the second, the outside repetitive elements, the third, the half of the elements in the interphase of the metalloid element, and the fourth, the half of the repetitive elements in the interphase.…”

Theoretical Calculation of Absolute Radii of Atoms and Ions. Part 1. The Atomic Radii

“…theoretical atomic radii are plotted as function of atomic number. Although the electronegativity is an atomic property and depends upon the atomic radii [36], it is not a directly measurable experimental quantity of an isolated atom and it has no quantum mechanical operator [6,37]. But the inverse relationship between the polarizability and hardness is well established [38].…”