Thallium atomic properties

For a discussion of the atomic properties of the group 13 metals see Downs AJ (1993) In Downs AJ (eds) Chemistry of aluminum gallium, indium and thallium. Blackie, London, Chapter 1... 

Our first study of these systems was the synthesis in 1998 of the polymeric complex [ 1( 6 5)2( )2] through the reaction between triphenylphosphine oxide, thallium nitrate and lithium bis(pentafluorophenyl)aurate(I) [71]. This complex consisted of an extended unsupported linear chain of alternate gold and thallium centers. These atoms displayed Au-Tl interactions of 3.0358(8) and 3.0862(8) A, and the thallium atoms showed a distorted pseudo-trigonal-bipyramidal environment, taking into account the stereochemically active inert pair of this atom. As described below, the environment around thallium is one of the main factors that affects the optical properties of these mixed systems. 

Thallium, atomic no. 81 This element is better known for its poisonous properties and links with almost undetected deaths and Agatha Christie -type murder mysteries.2 Thallium compounds are used in some countries as cheap insecticides, particularly for killing cockroaches. Intake of this element causes stomach pains, vomiting and nausea, painful soles and palms of hands, limb weakness, double vision, involuntary eye movements, hallucina tions, characteristic hair loss and white lines across the nails. The symptoms are often mis-diagnosed as other diseases. Treatment is with the chemical Prussian Blue... 

The related reaction shown in Equation (104)117 leads to a butterfly arrangement with two thallium ions bridging between two gold atoms, 127. Here, the Tl-Tl distance is 360.27 pm and is thought to contribute significantly to the physical properties of the complex. The compound shows solvent-dependent luminescent behavior in solution as well as in the solid state. 

Ununtrium is located on the periodic chart in group 13 (IIIA) just below thallium and indium. It is expected to have chemical and physical properties similar to these two homo-logues. Since only one or two unstable atoms of the isotopes of ununtrium have been synthesized, its melting point, boiling point, and density are not known. 

Uranium-238 emits an alpha particle to become an isotope of thorium. This unstable element emits a beta particle to become the element now known as Protactinium (Pa), which then emits another beta particle to become an isotope of uranium. This chain proceeds through another isotope of thorium, through radium, radon, polonium, bismuth, thallium and lead. The final product is lead-206. The series that starts with thorium-232 ends with lead-208. Soddy was able to isolate the different lead isotopes in high enough purity to demonstrate using chemical techniques that the atomic weights of two samples of lead with identical chemical and spectroscopic properties had different atomic weights. The final picture of these elements reveals that there are several isotopes for each of them. 

One of the classical properties of the main group elements is that the stability of the lower oxidation states increases with atomic number, and the chemistry of thallium is a good example of this effect. In aqueous solution, the Tl+ ion is stable with respect to oxidation by the solvent and there is accordingly an extensive chemistry of this oxidation state. The similarities between Tl+ and the corresponding alkali metal cations have resulted in much interest in the use of this ion as a probe in biochemical systems, and the ease with which 205T1 NMR spectra can be recorded has also had an impact on such studies.277,278... 

Of course, what the students are really interested in is why thallium is poisonous. Surprisingly, thallium is toxic because it mimics potassium in the body. But why would thallium behave like potassium As we study the periodic table and chemical periodicity, there is no immediate reason to suspect that these two elements would have similar properties. A close look at the electron shell arrangement of thallium and potassium, however, reveals that both form +1 ions. Since Tl+ ions also happen to be similar in size to K+ ions, they are able to replace potassium ions in cellular processes. (Thallium poisoning is treated with a compound called Prussian blue, which binds to +1 ions and thus facilitates their removal from the body.) It is clear then that we cannot understand the toxicity of thallium without studying its atomic structure and electron distribution. But chemistry is only part of the story. The effects of thallium poisoning only make sense if the... 

The atoms of the chemical elements, are, as I have already said, extremely complex, but their structure is not yet completely understood. To some part of each kind of atom its chemical properties and its spectrum are probably due. It is conceivable that this part may be the earliest to form, with its surrounding rings or envelopes at first not quite adjusted to permanent stability. With the final adjustment the isotopes as such should disappear, and the normal element be completed. This is speculation, and its legitimacy remains to be established. A careful comparison of the spectra of the elements from thallium up to uranium might furnish some evidence as to its validity. The spectrum of uranium, for example, may contain lines which really belong to some of its derivatives. 

Haider, N. C., R. J. Metzger, and C. N. J. Wagner Atomic Distribution and Electrical Properties of Liquid Mercury-Thallium Alloys. J. Chem. Phys. 45, 1259 (1966). 

Acyl hypohalites are usually prepared in situ by reaction of a metal salt of die carboxylic acid widi a halogen (equation 3). Classically the silver salt is used, but problems associated widi die preparation of dry silver carboxylates, as well as the more obvious economic factor, have led to the development of methods using mercury and thallium salts. Evidently, those functional groups which react readily widi halogens are not compatible with this approach. A major limitation of the acyl hypohalites is the readiness with which they transfer halogen atoms to alkyl radicals this property essend ly limits their use to decarboxylative halogenation reactions. 

Equation 4. Among the heavier elements in the B subgroup of the periodic table, thallium, lead, and bismuth are notable because their compounds resemble those of the elements with atomic numbers two lower thus the properties of Pb(II) compounds are similar to those of Hg(II) compounds, etc. (12). For this reason, we have chosen Pb(II) compounds as the principle bases for estimation of entropies of Hg(II) compounds with Equation 4. 

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