Electroneutrality rule, Pauling

The values of i calculated fromEq. 2.105 on v(M) in different molecules, give the average (for 700 molecular halides and chalcogenides) of e = 0.5e, in agreement with Pauling s famous Electroneutrality Rule [480,481] which states that net charges of atoms in stable molecules and crystals should not exceed Yi, even though later he softened this limitation to 1 [475]. This principle later has been proved theoretically, confirmed experimentally and now plays a key role in the description of electronic structure of molecules and crystals. 

One classical example that apphes the electroneutrality principle is the electronic structure of carbon monoxide, a diatomic molecule with a very small dipole moment of 0.110 debye. The only electronic structure that satisfies the octet rule for CO is C=0 , a structure that corresponds to C and O, if the shared electron pairs are equally devided by the two atoms. Pauling showed that the electronegativity difference of 1.0 would correspond to about 22% partial ionic character for each bond, and to charges of and 0° +. A second possible electronic structure, C=O , does not complete the octet for carbon. The partial ionic character of the bonds corresponds to C0.44+ If these two structures contribute... 

The course of modern organometallic chemistry has been greatly influenced by three simple generalizations the Dewar-Chatt-Duncanson synergic bonding model for metal-olefin complexes (40, 72) Pauling s electroneutrality principle (174), and the 18-electron or inert gas rule (202). In this section the impact of recent theoretical calculations on these important generalizations will be evaluated. 

In order for unsynchronous resonance to occur, the atoms M+ and M° must have an unoccupied orbital available so that they can accept an additional bond. M does not require such an unoccupied orbital because the electroneutrality principle rules out its accepting an additional bond, which would convert it to M2. Accordingly, the structural requirement for a system to possess metallic character is that the fraction of the atoms M+ and M° have available an unoccupied orbital, called the metallic orbital. The average value of 0.72 orbital per atom for the metallic orbital, as deduced from the Slater-Pauling curve, implies that, with unsynchronous resonance of the covalent bonds, the metal consists of 28% M+, 44% M°, and 28% M. ... 

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