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| Atomic symbol: Tl |
| Atomic number: 81 |
| Atomic weight: 204.37 |
| Atomic volume: 17.2 cm3/mol |
| Density: 11.85 g/cm3 |
| Period Number: 6 |
| Group number: 13 |
| Group name: Metal |
| Element classification: Metal |
| Phase at room temperature: Solid |
| Melting Point: 576.7 K |
| Boiling point: 1730 K |
| Heat of fusion: 4.142 kJ/mol |
| Heat of vaporization: 164.10 kJ/mol |
| Ionization Energy: 6.108 eV |
| 1st ionization energy: 589.4 kJ/mole |
| 2nd ionization energy: 1971 kJ/mole |
| 3rd ionization energy: 2878 kJ/mole |
| Electronegativity: 1.83 |
| Electron affinity: 20 kJ/mole |
| Specific heat: 0.13 J/gK |
| Heat atomization: 182 kJ/mole atoms |
| Shells: 2,8,18,32,18,3 |
| Electron Shell Configuration: [Xe] 4f14 5d10 6s2 6p1 |
| Minimum oxidation number: 0 |
| Maximum oxidation number: 3 |
| Minimum common oxidation number: 0 |
| Maximum common oxidation no: 3 |
Appearance & Characteristics |
| Structure:: hcp: hexagonal close pkd |
| Color: bluish-gray |
| Hardness: 1.2 mohs |
| Toxicity: ? |
| Characteristics: soft |
| Uses: IR detectors, photomult. |
| Reaction with air: mild, =>Tl2O |
| Reaction with 6M HCl: ? |
| Reaction with 15M HNO3: mild, =>TlNO3 |
| Reaction with 6M NaOH: ? |
| Number of isotopes: 2 |
| Oxide(s): Tl2O Tl2O3 |
| Hydride(s): ? |
| Chloride(s): TlCl TlCl3 |
| Atomic Radius: 170 pm |
| Ionic radius (1- ion): pm |
| Ionic radius (1+ ion): 164 pm |
| Ionic radius (2- ion): pm |
| Ionic radius (2+ ion): pm |
| Ionic radius (3+ ion): 102.5 pm |
| Thermal conductivity: 46.1 J/m-sec-deg |
| Electrical conductivity: 55.556 1/mohm-cm |
| Polarizability: 7.6 A^3 |
| Source: Zn/Pb smelting by-product |
| Relative abundance solar system: -0.735 log |
| Abundance earth's crust: -0.3 log |
| Estimated crustal abundance: 8.5×10-1 milligrams per kilogram |
| Estimated oceanic abundance: 1.9×10-5 milligrams per liter |
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| (Gr. thallos: a green shoot or twig) Thallium was discovered spectroscopically in 1861 by Crookes. The element was named after the beautiful green spectral line, which identified the element. The metal was isolated both by Crookes and by Lamy in 1862 at about the same time. |
| Thallium occurs in crooksite, lorandite, and hutchinsonite. It is also present in pyrites and is recovered from the roasting of this ore in connection with the production of sulfuric acid. It is also obtained from the smelting of lead and zinc ores. Extraction is somewhat complex and depends on the source of the thallium. Manganese nodules, found on the ocean floor, contain thallium. |
| When freshly exposed to air, thallium exhibits a metallic luster, but soon develops a bluish-gray tinge, resembling lead in appearance. A heavy oxide builds up on thallium if left in air, and in the presence of water the hydride is formed. The metal is very soft and malleable. It can be cut with a knife. Twenty five isotopic forms of thallium, with atomic masses ranging from 184 to 210 are recognized. Natural thallium is a mixture of two isotopes. A mercury-thallium alloy, which forms a eutectic at 8.5% thallium, is reported to freeze at -60C, some 20 degrees below the freezing point of mercury. |
| Thallium sulfate has been widely employed as a rodenticide and ant killer. It is odorless and tasteless, giving no warning of its presence. Its use, however, has been prohibited in the U.S. since 1975 as a household insecticide and rodenticide. The electrical conductivity of thallium sulfide changes with exposure to infrared light, and this compound is used in photocells. Thallium bromide-iodide crystals have been used as infrared optical materials. Thallium has been used, with sulfur or selenium and arsenic, to produce low melting glasses with become fluid between 125 and 150C. These glasses have properties at room temperatures similar to ordinary glasses and are said to be durable and insoluble in water. Thallium oxide has been used to produce glasses with a high index of refraction, and is used in the manufacture of photo cells. Thallium has been used in treating ringworm and other skin infections; however, its use has been limited because of the narrow margin between toxicity and therapeutic benefits. |
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