{"id":180,"date":"2020-04-09T09:47:12","date_gmt":"2020-04-09T09:47:12","guid":{"rendered":"https:\/\/thechemicalelements.com\/?page_id=180"},"modified":"2023-08-15T15:34:15","modified_gmt":"2023-08-15T15:34:15","slug":"thallium","status":"publish","type":"post","link":"https:\/\/thechemicalelements.com\/thallium\/","title":{"rendered":"Thallium (Tl)"},"content":{"rendered":"\n

Thallium is a chemical element with the atomic number 81 in the periodic table. It\u2019s a moderately abundant metal, found in trace amounts in Earth\u2019s crust. In fact, thallium is 10 times more abundant than silver<\/a>. Being a member of the aluminum family of periodic table elements, this post-transition metal has three valence electrons and is extremely toxic. Namely, this soft and easily melted substance has an especially strong effect on the central nervous system in humans, which can lead to paralysis and severe damage to the brain. <\/span><\/p>\n\n\n\n

Thallium-bearing minerals are rare in nature. The Alchar mine in the Republic of North Macedonia is the only location in the world where the thorium<\/a>-rich mineral <\/span>lorandite<\/span><\/a> occurs in its purest form. Scientists are especially intrigued by it as a geochemical detector of <\/span>solar neutrinos<\/span><\/i>. If the power of the Sun could be thoroughly understood with the help of lorandite, the scientists would be able to produce many other \u201c<\/span>mini-Suns<\/span><\/a>\u201d that would produce environmentally clean power for our planet.<\/span><\/p>\n\n\n\n

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Chemical and Physical Properties of Thallium<\/span><\/h3>\n\n\n\n
Property<\/strong><\/td>Value<\/strong><\/td><\/tr>
Symbol<\/td>Tl<\/td><\/tr>
Name<\/td>Thallium<\/td><\/tr>
Atomic number<\/td>81<\/td><\/tr>
Group<\/td>Metal<\/td><\/tr>
Period<\/td>6 (p-block)<\/td><\/tr>
Color<\/td>A bluish-white hued metal<\/td><\/tr>
Physical state<\/td>Solid at room temperature<\/td><\/tr>
Half-life<\/td>From 5.2(+30\u221214) milliseconds to 3.78 years<\/td><\/tr>
Electronegativity<\/td>2.04<\/td><\/tr>
Density<\/td>11.85 g.cm-3<\/td><\/tr>
Melting point<\/td>304\u00b0C, 579\u00b0F, 577 K<\/td><\/tr>
Boiling point<\/td>1473\u00b0C, 2683\u00b0F, 1746 K<\/td><\/tr>
Van der Waals radius<\/td>0.182 nm<\/td><\/tr>
Ionic radius<\/td>1.59 (+1) \u00c5<\/td><\/tr>
Atomic weight<\/td>204.3833<\/td><\/tr>
Isotopes<\/td>41<\/td><\/tr>
Most characteristic isotope<\/td>205Tl<\/td><\/tr>
Electronic shell<\/td>[Xe] 4f14 5d10 6s2 6p1<\/td><\/tr>
The energy of the first ionization<\/td>589.1 kJ.mol-1<\/td><\/tr>
The energy of the second ionization<\/td>1970.5 kJ.mol-1<\/td><\/tr>
The energy of the third ionization<\/td>2877.4 kJ.mol-1<\/td><\/tr>
Crystal Structure<\/td>Hexagonal<\/td><\/tr>
Shells<\/td>2,8,18,32,18,3<\/td><\/tr>
Valence<\/td>1,3<\/td><\/tr>
Covalent Radius<\/td>1.48 \u00c5<\/td><\/tr>
Atomic Radius<\/td>2.08 \u00c5<\/td><\/tr>
Atomic Volume<\/td>17.2 cm\u00b3\/mol<\/td><\/tr>
Name Origin<\/td>Greek: thallos (green twig)<\/td><\/tr>
Discovery date<\/td>1861<\/td><\/tr>
Discoverer<\/td>Sir William Crookes<\/td><\/tr>
Location of Discovery<\/td>England<\/td><\/tr>
Pronunciation<\/td>THAL-i-em<\/td><\/tr>
Oxidation States<\/td>3,(1)<\/td><\/tr>
Uses<\/td>Rat and ant poisons, detecting infrared radiation<\/td><\/tr>
Description<\/td>Very soft, malleable, ductile, blue-white shiny metal<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

With the periodic table symbol Tl, atomic number 81, atomic mass of X g.mol<\/span>-1<\/span>, and electron configuration [Xe] 4f<\/span>14<\/span>5d<\/span>10<\/span>6s<\/span>2<\/span>6p<\/span>1<\/span>, thallium is a soft, tasteless, odorless, malleable, and lustrous metal. Any sharp or hard object could make a dent in it. <\/span><\/p>\n\n\n\n

Thallium reaches its boiling point at 1473\u00b0C, 2683\u00b0F, 1746 K, while the melting point is achieved at 304\u00b0C, 579\u00b0F, 577 K. This member of the boron<\/a> family of elements in the periodic table has an electronegativity of 1.8 according to Pauling, whereas the atomic radius according to van der Waals is 0.182 nm. <\/span><\/p>\n\n\n\n

Element 81 has a hexagonal close-packed structure. When thallium reacts with nitric acid and sulfuric acid, it forms nitrate and sulfate salts. It dissolves slowly in both hydrochloric acid and diluted sulfuric acid, while this chemical reaction is more rapid in nitric acid.<\/span><\/p>\n\n\n\n

In its pure, elemental form, thallium metal appears gray in color, resembling the element tin in its physical appearance. However, when this post-transition metal is exposed to high temperature, it becomes discolored.<\/span><\/p>\n\n\n\n

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How Was Thallium Discovered?<\/span><\/h2>\n\n\n\n

In 1861, element 81 was independently discovered by the French chemist Claude-Auguste Lamy (1820-1878) and the British chemist and physicist Sir William Crookes (1832-1919).<\/span><\/p>\n\n\n\n

When, in 1850, Sir William Crookes attempted to extract selenium from a sample obtained from a sulfuric acid factory in Tilkerode, he observed a tellurium<\/a> concentration in the residue of the chemical reaction. A decade later, Sir Crookes conducted an experiment for which he needed some tellurium. The British chemist recalled that the selenium<\/a> isolation process resulted in some tellurium quantities as a residue, so he tried to recreate the chemical process. Strangely enough for him, this time he wasn\u2019t able to produce tellurium. <\/span><\/p>\n\n\n\n

Eager to get to the root of this chemical enigma, Sir Crookes applied the method of spectroscopic analysis in an effort to understand where the experiment went wrong. By the means of flame spectroscopy, he observed a bright green line in the spectrum that hadn\u2019t been seen before in any other known chemical element. Confident in his scientific results, Sir William Crookes published his findings in a journal he edited and published, called <\/span>Chemical News<\/span><\/i>.<\/span><\/p>\n\n\n\n

Despite being unable to discover all of thallium\u2019s physical and chemical properties, Sir Crookes succeeded in producing thallium salts that he showcased at the International Exhibition held in South Kensington, London, in 1862.<\/span><\/p>\n\n\n\n

As chance would want it, the French chemist Claude-Auguste Lamy was also attending the London exhibition. Since he succeeded in isolating thallium in larger quantities the same year, Lamy brought an ingot of pure thallium metal to the exhibition. By this, this French chemist became the first scientist to isolate the pure metal form of element 81.\u00a0<\/span><\/p>\n\n\n\n

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How Did Thallium Get Its Name?<\/span><\/h2>\n\n\n\n

The name <\/span>thallium <\/span><\/i>originates from the Greek word ‘<\/span>thallos<\/span><\/i>‘, meaning a \u2018<\/span>green shoot <\/span><\/i>or<\/span> green twig<\/span><\/i>\u2019. Sir William Crook chose this name for his new element, due to its characteristic green spectral line that serves as an identification mark of element 81.<\/span><\/p>\n\n\n\n

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Where Can You Find Thallium?<\/span><\/h2>\n\n\n\n

This post-transition metal is not a naturally occurring chemical. It can be found in granites, soils, and clays. Thallium also appears in metal-sulfide ores, pyrite, zinc<\/a>, lead, copper, as well as in minerals that contain the chemical elements silver, lead, copper<\/a>, arsenic<\/a>, antimony<\/a>, and other heavy-metal sulfide ores. <\/span><\/p>\n\n\n\n

While the mineral lorandite contains thallium in the purest form, there are also other thallium-bearing minerals, such as crookesite, sabatierite, routhierite, christite, bukovits, hutchinsonite, and gabrielite. Thallium obtained from these minerals requires a long process of isolation and purification than the thallium isolated from lorandite ore. <\/span><\/p>\n\n\n\n

The mineral lorandite can be found only in a mine located in the Republic of North Macedonia, while the gabrielite mineral is found in Switzerland. The mineral deposits in Nevada, United States, and China contain some quantities of the christite mineral. In addition, bukovite is the most dispersed thallium-bearing mineral and occurs in deposits in Argentina, Sweden, France, and the Czech Republic.<\/span><\/p>\n\n\n\n

For commercial purposes, thallium can be synthesized by smelting zinc and lead. It can also be obtained as a by-product of the sulphuric acid production process or extracted from dust from the smelter flues.<\/span><\/p>\n\n\n\n

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The Alchar Mine<\/span><\/h3>\n\n\n\n

The largest and richest concentration of thallium minerals in the world is found in the Alchar mine (<\/span>Macedonian:<\/span><\/i> \u0410\u043b\u0448\u0430\u0440) on <\/span>Kozuf<\/span><\/a>, a mountain with an untouched natural abundance of rare minerals as well as indigenous botanical and animal species. <\/span><\/p>\n\n\n\n

Dating back to the 14\u201315 centuries, this thallium mine is a low-temperature hydrothermal gold\u2013arsenic\u2013antimony\u2013thallium deposit, located in the heart of the southern Balkan country. Existing for more than <\/span>five millennia<\/span><\/a>, it was the only mine in the world where thallium was actively mined until World War II. <\/span><\/p>\n\n\n\n

The ancient mine is nowadays declared a protected site and it is accessible only to scientists working on the geochemical <\/span>LORAX project<\/span><\/a> that holds special approval from the North Macedonian government officials as well as from the Sts. Cyril and Methodius University in Skopje.\u00a0<\/span><\/p>\n\n\n\n

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List of Thallium Minerals<\/span><\/h3>\n\n\n\n

In 1894, the most common thallium-bearing mineral <\/span>lorandite<\/span><\/a> (lor\u00e1ndite) was first discovered by the Hungarian mineralogist J\u00f3zsef S\u00e1ndor Krenner in the Alchar mine, Republic of North Macedonia. By its composition, this mineral is a thallium arsenic sulfosalt (TlAsS<\/span>2<\/span>). It\u2019s assumed that this unique mineral was <\/span>formed<\/span><\/a> only at this place on our planet after an explosion on the Sun that has occurred around a billion years ago. Lorandite is considered to be one of the rarest minerals in the world.<\/span><\/p>\n\n\n\n

Apart from the lorandite as the main mineral in which element 81 occurs, thallium can be also traced in the following minerals:\u00a0<\/span><\/p>\n\n\n\n