Ionocovalent Bond is Binary Chemical Bond

Yonghe Zhang,

American Huilin Institute 


For a long time, the ionic and the covalent nature have been considered as the isolated or false dichotomy properties, and no quantitative correlations between the two.

The ionocovalent theory changed the old antagonistic qualitative relations of the ionic-versus-covalent dichotomy of bond nature. The ionic energy I(Z*,n*,Iz) is harmonized with covalent environment C(rc, rc-1,n*rc-1)  to form an unified new quantitative Ionocovalency (potential energy) continuum scale:


IC =. I(Z*,n*,Iz) I(Z*,n*,Iz)


It indicated that a compound consists of both the ionic nature and the covalent nature of its relative content components of the composition. In this scale, the ionic and the covalent are inverse sequence; the larger ionocovalency, the stronger the covalent, the weaker the ionic, vice versa (Ionocovalent Bond Parameters, Functions and Scales ) [1-3].   


Fig.1 Covalent radium 156 pm of LiF is smaller than that of Li

 Fig.2 The electrostatic forces between atom A (A1 and A2) and tom B(B1 and B2)

are not always the same. 



It should be noted that, so called “pure ionic bond” and "pure covalent bond" do not exist, as shown in Figure 1 [4], the covalent radius of 156pm of the most typical "pure" Ionic compounds LiF due to the covalent bond orbital overlap is smaller than the covalent radius of 252pm of Li atoms. And the so called “pure covalent bond” also actually not exists. As Hydrogen molecule, Figure 2 shows that in the actual molecule, due to the conjugation effect, steric hindrance conjugation effect, steric hindrance effects and adjacent group electronegativity effects, the same kind of bond length could be some differences and there could be some part of the ionic nature. The electrostatic forces between atom A (A1 and A2) and tom B(B1 and B2) are not always the same.  Metal bond is a non-localized covalent bond, and the hydrogen bond is not part of the chemical bond, only the intermolecular force. Thus, the ionocovalent bond is the binary chemical bond and the pure ionic and the pure covalent are the two extremes of the ionocovalent scaleat the end of each side.



[1]  Zhang, Y. Ionocovalency and Applications 1. Ionocovalency Model and Orbital Hybrid Scales.  Int. J. Mol. Sci. 2010, 11, 4381-4406. IC-Model Full-Text

[2] Zhang, YH.  Ionocovalent Theory , J. Am. Huilin. Ins. 2011, 5, 1-11

[3]  Zhang, Y. Electronegativities of Elements in Valence States and Their ...1 Electronegativities of  elements in valence states, Inorg. Chem.198221 (11), pp 3886–3889

[4]. Lower, S. Chemical bonds: covalent or ionic or what?. In Chem1 Virtual Textbook



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