Electron Conduction in Alkali Metals

Pauling has introduced a metallic orbital [54] in order to provide a VB representation for electron conduction in alkali metals. For lithium, this orbital is a 2pa AO, and use of it enables bicovalent VB structures such as 

The results of the calculations show that prior to electron transfer, the dominant structure is structure I. On delocalising an electron from the Liy(-) of structure I into either a LiA or a Lifi AO, structures II and III are calculated to have larger weights than has the bicovalent structure VII. 

We now demonstrate that, in the simplest treatment, it is more favourable energetically to delocalise an electron into an antibonding ct 2s MO rather than into the 2p AO. To do this, we have performed separate calculations using structures I-V, and I, IV, V and VII. The results (Table 1) show that 0.100 a.u. of energy is needed to transfer an electron from Liy( ) into the ct 2s MO whereas the Liy(-) — LiA(2p) delocalisation requires 0.114 a.u. 

Of course the above treatment is not definitive, but it does suggest that the antibonding a 2s MO mechanism can compare favourably with the pivotal resonance mechanism as the primary VB formulation for electron conduction in metallic lithium. 

One way to include the 2pOA as well as the 2s AOs in the antibonding MO mechanism involves an initial formulation of the wavefunction for the four valence-shell electrons of 

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Chapter 21 Base-Displacement Reactions and Electron Conduction in Alkali Metals... 

ELECTRONIC CONDUCTANCE OF ALKALI METALS DISSOLVED IN ALKALI HALIDES... 

Is the order of magnitude of your result consistent with the observed mobility If not, suggest an alternative model for electronic conductance of alkali metals in alkali metal salts. 

Electronic Conductance of Alkali Metals Dissolved in Alkali... 

Figure 1. Electron conduction in p and n type semiconductors, and alkali metals. (Cathode (-) on the left, anode (+) on the right.)...

Pauling has described the process of electron conduction in solid state alkali metals in terms of electron transfer from one metallic orbital into another... 

Bronstein and Bredig were the discoverers (1958) of the unexpected fact that 1% concentrations of alkali metals dissolved in molten salts show electronic conductivity. In the K-KCl system, the conductance was found to increase more than linearly with concentration while in the Na-NaCl system, it increases less than linearly. 

Attention should also be called to the presence of significant amounts of electronic conduction in some melts. The unambiguous detection of small amounts of this condition in the presence of the ionic conduction is relatively difficult, although well-conducted tests for non-Faradaic electrolysis is a possible means. More commonly, the magnitude of the electronic conductivity is sufficient that no doubt remains as to its source, although changes in the ionic portion are then quite obliterated. In pure salts this behavior is most frequently encountered with the molten oxides and sulfides and, in mixtures, with solutions of the alkali, alkaline earth, and rare earth metals in their molten halides. These properties are further discussed in Section V,A. 

The properties of the intercalation compound, potassium graphite, KCg, have been detailed in several review articles.34/35 The bonding in potassium graphite is described in terms of the limiting structure, K+Cg", and it is believed that the anion forms as a result of the transfer of an electron from the alkali metal to the conduction band of graphite. Novikov and Volpin35 have noted a similarity between aromatic radical-anions and alkali metal-graphite intercalation compounds. Their observation was based on inspection of reduction potentials of aromatic hydrocarbons relative to biphenyl, Table 9.2 ... 

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