Thallium
Chemists William Crookes and Claude-Auguste Lamy discovered thallium independently in 1861, in residues of sulfuric acid production.Both used the newly developed method of flame spectroscopy, in which thallium produces a notable green spectral line.Thallium, from Greek θαλλός, thallós, meaning "green shoot" or "twig", was named by Crookes.For instance, thallium(III) fluoride, TlF3, has the β-BiF3 structure rather than that of the lighter group 13 trifluorides, and does not form the TlF−4 complex anion in aqueous solution.Like the analogous silver compounds, TlCl, TlBr, and TlI are photosensitive and display poor solubility in water.[21] The stability of thallium(I) compounds demonstrates its differences from the rest of the group: a stable oxide, hydroxide, and carbonate are known, as are many chalcogenides.Thallium forms the stable [Tl(CH3)2]+ ion in aqueous solution; like the isoelectronic Hg(CH3)2 and [Pb(CH3)2]2+, it is linear.Crookes used it to make spectroscopic determinations for tellurium on selenium compounds deposited in the lead chamber of a sulfuric acid production plant near Tilkerode in the Harz mountains.[34] Claude-Auguste Lamy used a spectrometer that was similar to Crookes' to determine the composition of a selenium-containing substance which was deposited during the production of sulfuric acid from pyrite.Lamy had received this material from the sulfuric acid plant of his friend Frédéric Kuhlmann and this by-product was available in large quantities.[38] Thallium concentration in the Earth's crust is estimated to be 0.7 mg/kg,[39] mostly in association with potassium-based minerals in clays, soils, and granites.The major source of thallium for practical purposes is the trace amount that is found in copper, lead, zinc, and other heavy-metal-sulfide ores.[45] The United States Geological Survey (USGS) estimates that the annual worldwide production of thallium is 10 metric tonnes as a by-product from the smelting of copper, zinc, and lead ores.[39] Thallium is either extracted from the dusts from the smelter flues or from residues such as slag that are collected at the end of the smelting process.Since there are several small deposits or ores with relatively high thallium content, it would be possible to increase the production if a new application, such as a thallium-containing high-temperature superconductor, becomes practical for widespread use outside of the laboratory.Thallium salts were used in the treatment of ringworm, other skin infections and to reduce the night sweating of tuberculosis patients.Combined with sulfur or selenium and arsenic, thallium has been used in the production of high-density glasses that have low melting points in the range of 125 and 150 Celsius°.In these, the sodium iodide crystals are doped with a small amount of thallium to improve their efficiency as scintillation generators.It was used in the 20th century for measuring the density of minerals by the flotation method, but its use has discontinued due to the high toxicity and corrosiveness of the solution.It allows optimization of the lamp temperature and color rendering,[65][66] and shifts the spectral output to the green region, which is useful for underwater lighting.Chronic high level exposure to thallium through inhalation has been reported to cause nervous system effects, such as numbness of fingers and toes.[75] Up to 20 grams per day of Prussian blue is fed by mouth to the patient, and it passes through their digestive system and comes out in their stool.[76][77] According to the United States Environmental Protection Agency (EPA), artificially-made sources of thallium pollution include gaseous emission of cement factories, coal-burning power plants, and metal sewers.
ThuliumStandard atomic weightperiodic tableHydrogenHeliumLithiumBerylliumCarbonNitrogenOxygenFluorineSodiumMagnesiumAluminiumSiliconPhosphorusSulfurChlorinePotassiumCalciumScandiumTitaniumVanadiumChromiumManganeseCobaltNickelCopperGalliumGermaniumArsenicSeleniumBromineKryptonRubidiumStrontiumYttriumZirconiumNiobiumMolybdenumTechnetiumRutheniumRhodiumPalladiumSilverCadmiumIndiumAntimonyTelluriumIodineCaesiumBariumLanthanumCeriumPraseodymiumNeodymiumPromethiumSamariumEuropiumGadoliniumTerbiumDysprosiumHolmiumErbiumYtterbiumLutetiumHafniumTantalumTungstenRheniumOsmiumIridiumPlatinumMercury (element)BismuthPoloniumAstatineFranciumRadiumActiniumThoriumProtactiniumUraniumNeptuniumPlutoniumAmericiumCuriumBerkeliumCaliforniumEinsteiniumFermiumMendeleviumNobeliumLawrenciumRutherfordiumDubniumSeaborgiumBohriumHassiumMeitneriumDarmstadtiumRoentgeniumCoperniciumNihoniumFleroviumMoscoviumLivermoriumTennessineOganessonmercuryAtomic numbergroup 13 (boron group)Periodperiod 6Electron configurationMelting pointBoiling pointDensityHeat of fusionkJ/molHeat of vaporizationMolar heat capacityVapor pressureOxidation statesElectronegativityIonization energies