Ionocovalent Continuum

Yonghe Zhang

 American Huilin Institute,


Ionocovalency IC and the electronegativity XIC exhibit evidently the ionocovalency character. The greater the IC and the XIC, the more covalent and the less ionic the cation is, and vice versa. Generally, across the period, the more right-hand-side an element is, the more covalent it is. And the more down-ward an element is, the more ionic it is. The IC and XIC increase from the lower left to the upper right of the periodic table across the s and p blocks, and decrease down most columns. Trends parallel periodic trends in IE.

The ionocovalency is a continuum which is certainly an improvement over the old ionic-versus-covalent dichotomy. In so called ‘pure’ ionic bonding, an electron is transferred completely from one atom to another, once this transfer is complete, the IC potential will act to try to pull this electron back to its parent ion. If IC partially succeed then there will be some electron density, n*(Iav /R)½rc-1,in the region in between the ions, which is the situation in a covalent bond. Thus ‘pure’ ionic and ‘pure’ covalent bonds could be seen as two extremes of an IC continuum. And so a covalent scale has the ionic degree.

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