Thallium atoms, positions

Here the first term is the free energy of pure crystalline lead, the second term an assumed linear dependence on composition, and the third term the free energy of mixing lead and thallium in the atomic positions 0, J J, 0, J and J, J, 0 of the unit cube. Curves representing these expressions are shown in Fig. 7. The value of a... 

Using thallium—sodium zeolites of type X (n = 2.30), we observed an increase of adsorption capacity for water vapor and benzene at 38% replacement of sodium ions by thallium ions, and then its decrease with an increase in the degree of exchange. As thallium ions replace sodium ions in the position Sm (25) we may assume redistribution of cations at dehydration under the conditions of high vacuum and thermal treatment at 350°C, and stronger chemical bonds of thallium atoms in screened positions in comparison with sodium atoms. 

The compounds [CymB(Pz)3]Tl (136) and [FcB(Pz)3]Tl show polymeric structures, with bridging B(Pz)3 fragments in the solid state. This is a result of unfavorable steric interaction between the substituent on boron and the hydrogen atoms on the pyrazolyl ring 5-position. The structure of [Cym B(Pz)3]Tl is somewhat related, but it adopts a macrocyclic tetrameric structure rather than a linear polymeric structure. Ligands with secondary donors on the backbone may form additional bonds to the thallium atom. For example, in [HB(3-(2-pyridyl)Pz)3]Tl, weak TF"N interactions between pyridyl nitrogens and the T1 atom have been observed. HB(3-(2-MeOC6Fl4)Pz)3]Tl features close intramolecular TF 0 interactions. ... 

Obtain the valence-shell configuration of the thallium atom, Tl, using the position of this atom in the periodic table. 

The diffraction patterns for the eighteen samples with between 0 and 87-8 atomic percent thallium correspond in positions and relative intensities of the lines to the A1 arrangement. The photographs for 93-4 and 96-9 atomic percent thallium show this pattern, and in addition the lines of the room-temperature modification of thallium, which has the A 3 structure. The sample of pure thallium shows only the latter pattern. 

Another contribution is represented by an investigation of a cubic thallium cluster phase of the Bergmann type Na13(TlA.Cdi A.)27 (0.24 < x <0.33) (Li and Corbett 2004). For this phase too the body centred cubic structure (space group Im 3, a = 1587-1599 pm) may be described in terms of multiple endo-hedral concentric shells of atoms around the cell positions 0, 0, 0, and 14,14,14. The subsequent shells in every unit are an icosahedron (formed by mixed Cd-Tl atoms), a pentagonal dodecahedron (20 Na atoms), a larger icosahedron (12 Cd atoms) these are surrounded by a truncated icosahedron (60 mixed Cd-Tl atoms) and then by a 24 vertices Na polyhedron. Every atom in the last two shells is shared with those of like shells in adjacent units. A view of the unit cell is shown in Fig. 4.38. According to Li and Corbett (2004), it may be described as an electron-poor Zintl phase. A systematic description of condensed metal clusters was reported by Simon (1981). 

Lithiation and mercuration are directed by the oxygen atom and occur at the 4-position, but thallation, achieved by treatment of dibenzofuran with thallium(III) isobutyrate at 110°C, affords the 2-thallium di(isobutyrate), which may be converted to the 2-iodo compound by reaction with iodine. Mercuration is achieved by treatment of dibenzofuran with mercuryfll) acetate at 150°C, and the resultant 4-mercuric acetate (56%) may also be converted to the iodo compound. ... 

From the late 1960s onwards, a number of research groups around the world began to investigate alternatives to pneumatic nebulization for sample introduction, in an attempt to overcome transport efficiency limitations. The most successful approaches were those which involved heating small, discrete liquid samples, and sometimes even solid samples, directly on a metal filament, boat, or cup which could be positioned reproducibly into a flame. However, since the temperature of the metal would be lower than that of the flame itself, the techniques were confined to the determination of relatively easily atomized elements such as arsenic, bismuth, cadmium, copper, mercury, lead, selenium, silver, tellurium, thallium, and zinc. 

The thallium(i) polysulphide TI2S5 has a structure in which the two negative charges in the 85 ion are localized at the end two S atoms. The Tl atoms are three-co-ordinate and pyramidal, so here the lone pair is sterochemically active, occupying the fourth tetrahedral position. 

In both cases the tetrahedra around I are centered by atoms (Fig. 5). In T13VS4 the thallium ions occupy the J position the first coordination sphere is a rhombically deformed tetrahedron and the second one a tetrahedron too. Both together form a distorted rhombic antiprism (8a). 

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