Hyperelectronic elements

Several structural features, including electron transfer between atoms of different electronegativity, oxygen deficiency, and unsynchronized resonance of valence bonds, as well as tight binding of atoms and the presence of both hypoelectronic and hyperelectronic elements, cooperate to confer metallic properties and high-temperature superconductivity on compounds such as (Sr.Ba.Y.LahCuO,-,. 

A review of the unsynchronized-resonating-covalent-bond theory of metals in presented. Key concepts, such as unsynchronous resonance, hypoelectronic elements, buffer elements, and hyperelectronic elements, are discussed in detail. Application of the theory is discussed for such things as the atomic volume of the constituents in alloys, the structure of boron, and superconductivity. These ideas represent Linus Pauling s understanding of the nature of the chemical bond in metals, alloys, and intermetallic compounds. 

A further complication exists for the hyperelectronic elements, namely the competition between the energy of stabilization of the substance afforded by the extra covalent bonds of the non-metallic form (with valence 1.44 greater than that for the metallic form) and that afforded by the extra resonance energy for the metallic form. Empirically it is observed that these two contributions are nearly equal for Sn. For the elements above and to the right of Sn, the non-metallic form is the more stable one for those and to the left, the metallic form is the more stable one. 

The discussion of metallic valence and of electron transfer from hyperelectronic elements to hypoelectronic elements for metals, both in bulk alloys and on surfaces, is complicated somewhat by the need for consideration of the effect of the metallic orbital. As pointed out earlier, the metallic orbital, 0.72 per atom, on average, is required for the unsynchronized resonance of valence bonds characteristic of metals. For example, tantalum is hypoelectronic and copper is hyperelectronic, and accordingly, electron transfer from copper to tantalum is expected, leading to an increase in valence for both Ta and Cu and to increased strength of bonds [29]. This increased strength of bonds shows up in bulk alloys as an effect independent of the electron transfer induced by difference in electronegativity. 

ABSTRACT The statistical treatment of resonating covalent bonds in metals, previously applied to hypoelectronic metals, is extended to hyperelectronic metals and to metals with two kinds of bonds. The theory leads to half-integral values of the valence for hyperelectronic metallic elements. 

For the case of hyperelectronic metals, that is, a substance composed of elements for which the number of outer electrons is greater than the number of outer orbitals, not including the metallic orbital, the statistical treatment is somewhat more complicated [34]. Let us first consider the valence v of such a metal. The neutral atoms M° form z bonds, and the ions M+ and M- form 2 I- 1 bonds. Denote the fractions of M+, M°, and M- by y., x, and y, respectively. Then from eqn. (4) the ratio of the number of neutral atoms to the number of ions, x/y, is given by... 

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