Thallium

Thallium is used in manufacturing electronics, pharmaceuticals and glass. It is highly toxic and has been used in rat poisons and insecticides. Thallium is soft and malleable at room temperature.  **Atomic Number:**81

 **Symbol:** Tl Thallium can be defined as "a soft, malleable, highly toxic metallic element, used in photocells, infrared detectors, low-melting glass, and formerly in rodent and ant poisons." (Science Element).
 * Atomic Weight:** 204.3833
 * Discovery:** Crookes 1861
 * Electron Configuration:**[Xe] 4f14 5d10 6s2 6p1
 * Element Classification:** __ [|metal] __
 * Discovered By:** Sir William Crookes
 * Discovery Date:** 1861 (England)
 * Name Origin:** Greek: thallos (green twig), named for a bright green line in its spectrum.
 * Density (g/cc):** 11.85
 * Melting Point (°K):** 576.6
 * Boiling Point (°K):** 1730
 * Appearance:** soft bluish-gray metal
 * Atomic Radius (pm):** 171
 * Atomic Volume (cc/mol):** 17.2
 * Covalent Radius (pm):** 148
 * Ionic Radius:** 95 (+3e) 147 (+1e)
 * Specific Heat (@20°C J/g mol):** 0.128
 * Fusion Heat (kJ/mol):** 4.31
 * Evaporation Heat (kJ/mol):** 162.4
 * Thermal Conductivity:** 46.1 J/m-sec-deg
 * Debye Temperature (°K):** 96.00
 * Pauling Negativity Number:** 1.62
 * First Ionizing Energy (kJ/mol):** 588.9
 * Oxidation States:** 3, 1
 * Lattice Structure:** __ [|hexagonal] __
 * Lattice Constant (Å):** 3.460
 * Lattice C/A Ratio:** 1.599
 * Uses:** infrared detectors, photomultipliers, rat poison, ant killer  

Thallium was discovered spectroscopically by Sir William Crookes, an English chemist, in 1861. Crooks had obtained the sludge left over from the production of sulfuric acid (H2SO4) from a friend. After removing all of the selenium from the sludge, he inspected it with a device known as a spectroscope to look for signs of tellurium. Rather than seeing the yellow spectral lines produced by tellurium, he observed a bright green line that no one had ever seen before. He named the new element that was producing the green line thallium, after the greek word for 'green twig', thallos. He isolated samples of thallium the next year. Thallium is found in the minerals crooksite (CuThSe), lorandite (TlAsS2) and hutchinsonite ((Pb, Tl)2As5S9), but is usually obtained as a byproduct of the production of sulfuric acid or as a byproduct of refining zinc or lead. There are no uses for metallic thallium since pure thallium quickly combines with oxygen and water vapor from the atmosphere, forming a black, powdery substance. Thallium, used in conjunction with sulfur or selenium and arsenic, forms low melting glass. Thallium sulfate (Tl2SO4), an odorless, tasteless thallium compound, was once used as a rat and ant poison, although it has been banned from household use in the United States since 1974. Thallium sulfide (Tl2S), thallium iodide (TlI) and thallium bromide (TlBr) are all compounds used in devices to detect infrared radiation.
 * Atomic Number:** 81
 * Atomic Weight:** 204.3833
 * Melting Point:** 577 K (304°C or 579°F)
 * Boiling Point:** 1746 K (1473°C or 2683°F)
 * Density:** 11.8 grams per cubic centimeter
 * Phase at Room Temperature:** Solid
 * Element Classification:** Metal
 * Period Number:** 6 **Group Number:** 13 **Group Name:** none
 * What's in a name?** From the Greek word for a green shoot or twig, **thallos**.
 * Say what?** Thallium is pronounced as **THAL-ee-em**.
 * History and Uses:**
 * Estimated Crustal Abundance:** 8.5×10-1 milligrams per kilogram
 * Estimated Oceanic Abundance:** 1.9×10-5 milligrams per liter
 * Number of Stable Isotopes:** 2 (View all isotope data)
 * Ionization Energy:** 6.108 eV
 * Oxidation States:** +3, +1

An example of where one could be able to find thallium would be in the Earth's crust, and oddly enough thallium can be found in cigarette smoke.