| Thallium - Tl
CAS: 7440-28-0 Description: Soft, bluish-gray metal that looks like lead Classification: Other Metals Date of Discovery: 1861 Discoverer: Sir William Crookes Name Origin: Greek thallos, "a green shoot or twig" |
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Atomic Number: 81
Number of Neutrons: 123 Atomic Mass: 204.3833(2) amu Melting Point: 304 °C Boiling Point: 1473 ± 10 °C Density (293 K): 11.85 g/cm3 Atomic volume: 17.2 cm3/mol Electrical resistivity: 0.0617 10-6/cm 
Thermal conductivity: 0.461 W/cmK Enthalpy of atomization: 179.9 kJ/mol Enthalpy of vaporization: 164.10 kJ/mol Enthalpy of fusion: 4.142 kJ/mol Specific heat capacity: 0.13 J/gK |
Energy levels: 2-8-18-32-18-3
Electron configuration: [Xe]4f 145d106s26p1 Crystal Structure: Hexagonal Atomic radius: 2.08 Å Covalent radius: 1.48 Å Oxidation States: +1, +3 Electronegativity, Pauling: 2.04 Electron affinity: 0.2 eV First ionization energy: 6.108 eV 2nd ionization energy: 20.428 eV 3rd ionization energy: 29.829 eV Polarizability: 7.5 10-24cm3 |
| Isotope | Natural Abundance | Atomic Mass | Half-life | Decay Mode | Spin |
| 179Tl | 178.9917 | 0.2 s |  |
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| 182Tl | 181.9856 | 3 s |  +, EC |
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| 183mTl | 0.06 s | |
9/2- | ||
| 183Tl | 182.9826 | 5 s | +, EC |
1/2+ | |
| 184Tl | 183.9818 | 11 s | +, EC; |
1/2+ | |
| 185mTl | 1.8 s | IT; |
(9/2-) | ||
| 185Tl | 184.9791 | 20 s | EC, + |
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| 186mTl | 4 s | IT | |||
| 186Tl | 185.9776 | 28 s | +, EC |
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| 187mTl | 15.6 s | IT | (9/2+) | ||
| 187Tl | 186.9762 | 50 s | +, EC |
1/2+ | |
| 188mTl | 1.18 m | +, EC |
(7+) | ||
| 188Tl | 187.9759 | 1.2 m | +, EC |
(2-) | |
| 189mTl | 1.4 m | +, EC |
(9/2-) | ||
| 189Tl | 188.9743 | 2.3 m | +, EC |
(1/2+) | |
| 190mTl | 3.7 m | +, EC |
(7+) | ||
| 190Tl | 189.9738 | 2.6 m | +, EC |
(2-) | |
| 191mTl | 5.2 m | +, EC |
(9/2+) | ||
| 191Tl | 190.9723 | (1/2) | |||
| 192mTl | 10.8 m | +, EC |
(7+) | ||
| 192Tl | 191.972 | 9.6 m | +, EC |
(2-) | |
| 193mTl | 2.1 m | IT | (9/2-) | ||
| 193Tl | 192.9706 | 22 m | +, EC |
(1/2+) | |
| 194mTl | 32.8 m | +; EC |
(7+) | ||
| 194Tl | 193.9711 | 34 m | +, EC |
2- | |
| 195mTl | 3.6 s | IT | 9/2- | ||
| 195Tl | 194.9697 | 1.16 h | EC; + |
1/2+ | |
| 196mTl | 1.41 h | +, EC |
(7+) | ||
| 196Tl | 195.9705 | 1.84 h | +; EC |
2- | |
| 197mTl | 0.54 s | IT; +- |
9/2- | ||
| 197Tl | 196.96954 | 2.83 h | +; EC |
1/2+ | |
| 198mTl | 1.87 h | +, EC; IT |
7+ | ||
| 198Tl | 197.9405 | 5.3 h | EC, + |
2- | |
| 199Tl | 198.9698 | 7.4 h | EC | 1/2- | |
| 200Tl | 199.97095 | 1.087 d | EC | 2- | |
| 201Tl | 200.97080 | 3.040 d | EC | 1/2+ | |
| 202Tl | 201.97209 | 12.23 d | EC | 2- | |
| 203Tl | 29.524(14) | 202.972329 | Stable | 1/2+ | |
| 204Tl | 203.973848 | 3.78 y | -; EC |
2- | |
| 205Tl | 70.476(14) | 204.974412 | Stable | 1/2+ | |
| 206mTl | 3.76 m | IT | 12- | ||
| 206Tl | 205.976095 | 4.20 m | - |
0- | |
| 207mTl | 1.3 s | IT | 11/2- | ||
| 207Tl | 206.97741 | 4.77 m | - |
1/2+ | |
| 208Tl | 207.982004 | 3.053 m | - |
(5+) | |
| 209Tl | 208.98535 | 2.16 m | - |
(1/2+) | |
| 210Tl | 209.99006 | 1.30 m | - |
(5+) | |
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Thallium was discovered spectroscopically in l861 by Crookes. The element was named after the beautiful green spectral line, which identified the element. The metal was
isolated both by Crookes and Lamy in 1862 about the same time. Thallium occurs in crooksite [Cu7(Tl,Ag)Se4], lorandite (TlAsS2), and hutchinsonite [(Pb,Tl)2As5S9]. 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 hydroxide is formed. The metal is very soft and malleable. It can be cut with a knife. Forty-seven isotopic forms of thallium, with atomic masses ranging from 179 to 210 are recognized. Natural thallium is a mixture of two isotopes. The element and its compounds are toxic and should be handled carefully. Contact of the metal with skin is dangerous, and when melting the metal adequate ventilation should be provided. Thallium is suspected of carcinogenic
potential for man. 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 which become fluid between 125 and 150 ° C. 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. 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. A mercury-thallium alloy, which forms a eutectic at 8.5% thallium, is reported to freeze at -60 °C, some 20 degrees below the freezing point of mercury.
LINKS: Drinking Water Regulations: Thallium The Element Thallium Thallium: Clinical Applications Return
Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998. |
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