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Thallium (Tl)
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Thallium 81Tl204.3833
Thallium was discovered in 1861 by William Crookes at London, England. Isolated in 1862 by C. A. Lamy at Paris, France.
[Greek, thallos = green twig]
French: thallium
German: Thallium
Italian: tallio
Spanish: talio
Description: Thallium is a soft, silvery-white metal, which tarnishes readily in moist air and reacts with steam to form TlOH. It is attacked by acids, rapidly so by HNI3. Thallium is little used because of its toxicity, but is still employed in special types of glass.
Further Materials properties
| Crystal structure: |
(cell dimensions/pm), space group, |
|---|---|
| X-ray diffractions mass absorption coefficients: | CuKa 224 (µ/r) / cm2g-1 MoKa 119 (µ/r) / cm2g-1 |
| Neutron scattering length: | 0.8776 b/10-12 cm |
| Thermal neutron capture cross-section: | 3.43 sa / barns |
| Density: | 11 850 kg/m-3 [293 K] |
| Melting point: | 303.55°C / 576.7°K |
| Boiling point: | 1456.85°C / 1730°K |
| Molar volume: | 17.24 cm3 |
| Thermal conductivity: | 46.1 [300 K] W m-1K-1 |
| Coefficient of linear thermal expansion: | 28 x 10-6 K-1 |
| Electrical resistivity: | 18 x 10-8 [295 K] Ωm |
| Mass magnetic susceptibility: | -3.13 x 10-9(s) kg-1m3 |
| Radi: | Tl3+ 105; Tl+ 149; atomic 170; covalent 155 |
| Electronegativity: | 1.62 (TlI) 2.04 (TlIII) (Pauling); 1.44 (Allred); 3.2 eV (absolute) |
| Effective nuclear charge: | 5.00 (Slater); 12.25 (Clementi); 13.50 (Froese-Fischer) |
| Number of Isotopes (incl. nuclear isomers): | 41 |
| Isotope mass range: | 184 -> 210 |
Biological data
| Biological role: | None. |
|---|---|
| Toxicity | |
| Toxic intake: | metal, oral, human = 5.7 mg Kg-1 |
| Lethal intake: | ingestion of 0.2 - 1g Tl2SO4 for humans. LD50 (Tl2SO4, oral, mouse) = 29 mg Kg-1 |
| Hazards: | Thalium compounds are extremely toxic and cumulative; they are also absorbed through the skin. Thallium takes several days to act and affects the nervous system. It is also teratogenic. |
| Level in humans | |
| Blood: | 0.00048 mg dm-3 |
| Bone: | 0.002 ppm |
| Liver: | 0.004 - 0.033 ppm |
| Muscle: | 0.07 ppm |
| Daily dietary intake: | 0.0015 mg |
| Total mass of element in average [70 kg] person: |
0.5 mg |
Geological data
| Minerals: | Thallium minerals are rare, but the element is dispersed in potassium minerals such as sylvite and the caesium mineral pollucite. | |||
|---|---|---|---|---|
| Mineral | Formula | Density | Hardness | Crystal apperance |
| Crookesite | Cu7TlSe4 | 6.9 | 2.5 - 3 | tet., metallic grey |
| Hutchinsonite | (Tl,Pb)2As5S9 | 4.6 | 1.5 - 2 | orth., adam. red |
| Lorandite | TlAsS2 | 5.53 | 2 - 2.5 | mon., met. adamantine red/grey |
| Thalcusite | Cu3FeTl2S4 | 6.54 | 2.5 | tet., metallic grey |
| Chief ores: | thallium is generally obtained as the by-product of zinc and lead smelting. |
|---|---|
| World production: | 30 tonnes/year |
| Main mining areas: | see zinc and lead |
| Reserves: | n/a |
| Specimen: | available as granules. Danger! |
| Abundances | |
|---|---|
| Sun: | 8.0 (relative to H = 1 x 1012) |
| Earth's crust: | 0.6 ppm |
| Seawater | 1.4 x 10-5 |
| Residence time: | 10 000 years |
| Classification: | accumulating |
| Oxidation state: | I |
Source: Emsley, J. (1998) The Elements (3rd Edition)
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