Thallium interatomic distance

Alloys of lead and thallium have a structure based upon cubic closest packing from 0 to about 87-5 atomic percent thallium. The variation of the lattice constant with composition gives strong indication that ordered structures PbTl, and PbTl, exist. In the intermediate ranges, solid solutions of the types Pb(Pb,Tl)a and Pb(Pb,Tl)TlB exist. Interpretation of interatomic distances indicates that thallium atoms present in low concentration in lead assume the same valence as lead, about 2-14, and that the valence of thallium increases with increase in the mole fraction of thallium present, having the same value, about 2-50, in PbTls and PbTl, as in pure thallium. A theory of the structure of the alloys is presented which explains the observed phase diagram,... 

It is possible to discuss the interatomic distances in relation to the valences of lead and thallium. From the system of metallic radii (Pauling, 1949) and the relation =DX-0-600 log n... 

Most chemical reactions in the natural surroundings and in the chemical industrial processes take place in solution, and this aggregation state constitutes the main field of interest for the majority of chemists and biochemists. However, in contrast to the large number of detailed crystal structures, the amount of available structural information for species in solution is limited. The reason for this situation is certainly the inherent disorder of the solution state, from which follows the lack of an experimental method as hard as the single-crystal X-ray diffraction technique. Certainly, spectroscopic methods can be used for studies of symmetry and bonding properties, but in order to obtain accurate interatomic distances diffraction techniques (or EXAFS, extended X-ray absorption fine structure) have to be used. These techniques are not always easily accessible and have some weak points however, they are the only ones able to provide the latter type of structural data. In the following, the few reported (and one unpublished) studies of this type of thallium species in aqueous solution will be discussed. 

Fig. 8. Model of the structure of thallium(I) carboxylate species in highly concentrated aqueous solutions. Temperature = 25°C. (a) Formate species. [Tl]t t = 10.8 M, [H2O]/ [TKD] = 2.6, [formate ]/[Tl(I)] = 1.0. Thalliumd) ions are fourfold coordinated by three formate oxygens and one weakly bound water molecule (not shown), (b) Malonate species. [TlJtot = 9-0 M, [H20]/[T1(D] = 3, [malonate "]/[Tl D] = 0.5. Fourfold oxygen coordination of thalliumd) ion is shown only for one T1(I) atom. Some interatomic distances are given (in angstroms). From Yamaguchi et al. 177).

Fig. 9. Proposed structures and the determined interatomic distances (in angstroms) for thallium(IH) chloro complexes in aqueous solution. The water oxygens are dark, the Cl atoms shaded. Reprinted from Blixt et al. (145). Copyright 1995 American Chemical Society.

There is also a lot of structural information for other thallium(III) compounds (e.g., organothallium compounds), which has been obtained from the spin-spin coupling pattern of their NMR spectra. However, no interatomic distances have been obtained in this way. 

Group 13 Metals - Aluminum, Gallium, Indium, Thallium 133 Table 3.7. Interatomic distances in gallium-arsenic supermolecules. 

Lead, together with iridium and thallium, forms a group of close-packed metals isolated from the other close-packed metals, in that the interatom distances in iridium, thallium and lead are very large compared with those of neighbouring elements. ... 

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