Evaluation of Electronegativity Scales

A network-based correlation research between element electronegativity and node importance

Abstracted from real compounds, chemical elements can be considered a system tied by chemical bonds (or bonding relationships) between two elements, namely the chemical element and chemical bond system. Then, elements, bonds and their properties can be studied from the view of complex networks. Based on the previous work, we introduce bond polarity to judge edge direction and select four electronegativity scales to build the directed chemical bond networks. Taking node importance and element electronegativity as an example, we discuss the relationships of properties between chemistry and networks. Through quantitative analysis, the importance scale changing trends in all networks are found to follow the similar periodic laws. And there exist statistically significant correlations between most of scale pairs. The further analysis proves the similar chemical meanings between above two scales. All these conclusions are unassociated with specific electronegativity scales, even if their networks have different nodes and edges, which prove the rationality and universality of the proposed method. Our research gives a network explanation on element electronegativity, and we can study more objects and chemical properties from the view of complex networks.

Energy Electronegativity and Chemical Bonding

Historical development of the concept of electronegativity (EN) and its significance and prospects for physical and structural chemistry are discussed. The current cutting-edge results are reviewed: new methods of determining the ENs of atoms in solid metals and of bond polarities and effective atomic charges in molecules and crystals. The ENs of nanosized elements are calculated for the first time, enabling us to understand their unusual reactivity, particularly the fixation of N₂ by nanodiamond. Bond polarities in fluorides are also determined for the first time, taking into account the peculiarities of the fluorine atom's electronic structure and its electron affinity.

Cardinal Electronegativity Values Correlate with Physicochemical Properties

The use of the difference in electronegativity (EN) function is shown to be fundamentally untenable for differentiating ionic from covalent bonding in binary compounds. Also, the commonly used parameters of differences and averages of EN values do not provide a direct correlation with metallic, ionic, or covalent chemical bonding types. On the other hand, the cardinal coordinates of lower and higher EN values readily demonstrate such a correlation. Graphs and similar tables of these two parameters show how chemical bonding combines and separates a mixture of these three bonding types. The orthogonal axes of these two cardinal functions indicate that there are two separate contributors to bonding: a band-gap (conductive) and a polarity (insulative) component that together produce the variety of chemical bonding types. These characteristics arise from absolute and differential electronic potentials. This two-dimensional perspective provides the means for interpreting the nature of EN.

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

In this work, we propose a new representative electronegativity scale χ_DC based on a statistical analysis of 11 electronegativity scales associated with electric ionic resonance energy, ionization potential, electron affinity, polarizability, electric force, average orbital energy, chemical potential, electrochemical reduction potential, and electric potential energy. Among these scales, it is the new PE° electronegativity scale, which relates the reduction potential E° to Pauling's electronegativity scale. The scale χ_DC gives more weight to the physicochemical factors, which influence the electronegativity, but this scale is not necessarily the best electronegativity scale for the element. This scale is based on (1) the average of the experimental electronegativity values; (2) the proximity of an experimental value to the average given by the difference and the ratio to this average; (3) in critical cases, the periodicity network of the periods and the groups; and (4) the periodicity of the sequence of the ratios of the experimental electronegativity values to the best-selected electronegativity value. We have also taken as probe scales Nagle's, Allred and Rochow's, Allen's (Hoffman's and Politzer's), PE°, Gordy's, and Ghosh's electronegativity scales in order to investigate the trend of the physicochemical factors which influence the electronegativity. With this trend, we have determined zones where a physicochemical property influences the electronegativity more. We have also found that physicochemical perturbations such as the orbital overlap, the stable configurations, the nephelauxetic effect, the width of the band gap, the ligand field stabilization energy, the penetration of the orbitals, and the lattice energy influence the electronegativity. Besides, we have analyzed the exactness of the electronegativity of the scales through the periodical ranking, the chemical tripartite separation among ionic, covalent, or metallic bond (taking into account the amplitude of the metalloid band), and the physicochemical property of bond force. The representative χ_DC electronegativity scale is the best in periodicity, followed by Batsanov's and Pauling's scales. In the type of chemical bond, the ranking depends on the number and kind of compounds in the sample, but in general, Pauling's, the ARS, and Batsanov's electronegativity scales are the best with a confidence interval of 95%. On the other hand, in the physical bond force, Batsanov's, Pauling's, Mulliken's, Nagle's, Allen's, the ARS, and the χ_DC electronegativity scales are the best scales. Also, we have considered the free atom and the in situ hypotheses of electronegativity and used the low and high oxidation states to verify these hypotheses. Besides, as an example of the utility of this ranking of scales, we have analyzed the relation of lanthanum La and lutetium Lu to Group 3, lanthanides, and hafnium Hf. We also analyze the vertical, horizontal, Knight's move, and isodiagonal periodicity of the electronegativity and associate this periodicity to a similar chemical-physical behavior of elements or ions.