{"id":168,"date":"2020-04-09T09:44:34","date_gmt":"2020-04-09T09:44:34","guid":{"rendered":"https:\/\/thechemicalelements.com\/?page_id=168"},"modified":"2023-08-15T15:58:05","modified_gmt":"2023-08-15T15:58:05","slug":"indium","status":"publish","type":"post","link":"https:\/\/thechemicalelements.com\/indium\/","title":{"rendered":"Indium (In)"},"content":{"rendered":"\n

Indium is a chemical element with atomic number 49 in the periodic table<\/a>. It occurs in quantities of around 0.1 parts per million (ppm) in Earth\u2019s crust, and it\u2019s a member of the aluminum family with amphoteric properties. The outer shell electrons of indium adopt the oxidation states +1, +2, or +3 when forming compounds with other chemicals.\u00a0<\/span><\/p>\n\n\n\n

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Chemical and Physical Properties of Indium<\/span><\/h3>\n\n\n\n
Property<\/strong><\/td>Value<\/strong><\/td><\/tr>
Symbol<\/td>In<\/td><\/tr>
Name<\/td>Indium<\/td><\/tr>
Atomic number<\/td>49<\/td><\/tr>
Group<\/td>Metal<\/td><\/tr>
Period<\/td>5<\/td><\/tr>
Color<\/td>A lustrous silvery-white metal<\/td><\/tr>
Physical state<\/td>Solid at room temperature<\/td><\/tr>
Half-life<\/td>From 5 milliseconds to 4.41\u00d71014 years<\/td><\/tr>
Electronegativity<\/td>1.78<\/td><\/tr>
Density<\/td>7.31 g.cm-3 at 20\u00b0C<\/td><\/tr>
Melting point<\/td>156.60\u00b0C, 313.88\u00b0F, 429.75 K<\/td><\/tr>
Boiling point<\/td>2027\u00b0C, 3681\u00b0F, 2300 K<\/td><\/tr>
Van der Waals radius<\/td>0.162 nm<\/td><\/tr>
Ionic radius<\/td>0.80 nm (+3)<\/td><\/tr>
Atomic weight<\/td>114.818 g.mol-1<\/td><\/tr>
Most characteristic isotope<\/td>113In and 115In<\/td><\/tr>
Electronic shell<\/td>[Kr] 4d10 5s2 5p1<\/td><\/tr>
The energy of the first ionization<\/td>558.2 kJ.mol-1<\/td><\/tr>
The energy of the second ionization<\/td>1820.2 kJ.mol-1<\/td><\/tr>
The energy of the third ionization<\/td>2704 kJ.mol-1<\/td><\/tr>
Discoverer<\/td>Ferdinand Reich and Hieronymous Richter<\/td><\/tr>
Year<\/td>1863<\/td><\/tr>
Location<\/td>Germany<\/td><\/tr>
Pronunciation<\/td>IN-di-em<\/td><\/tr>
Oxidation States<\/td>3<\/td><\/tr>
Uses<\/td>Used to coat high speed bearings and as an alloy that lowers the melting point of other metals. Relatively small amounts are used in dental items and in electronic semiconductors.<\/td><\/tr>
Description<\/td>Silvery-white, soft, malleable and ductile metal.<\/td><\/tr>
Crystal Structure<\/td>Tetragonal<\/td><\/tr>
Shells<\/td>2,8,18,18,3<\/td><\/tr>
Valence<\/td>1,2,3<\/td><\/tr>
Covalent Radius<\/td>1.44 \u00c5<\/td><\/tr>
Atomic Radius<\/td>2.00 \u00c5<\/td><\/tr>
Atomic Volume<\/td>15.7 cm\u00b3\/mol<\/td><\/tr>
Name Origin<\/td>Latin: indicum (color indigo), the color it shows in a spectroscope.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Classified under the In symbol in the periodic table, with an atomic number 49, atomic mass of 114.82 g.mol<\/span>-1<\/span>, and <\/span>electron configuration [Kr] 4d<\/span>10<\/span>5s<\/span>2<\/span>5p<\/span>1<\/span>, the chemical element indium is a soft, ductile, corrosion-resistant, and malleable metal with a plasticky feel to it. <\/span><\/p>\n\n\n\n

With its lustrous silvery-white color, it resembles tin in appearance. Easily workable, indium metal can be shaped in many ways and dented with any slightly sharp object. Apart from the alkalis, indium is the softest metal in the periodic system of elements. In fact, even lead<\/a> is harder than indium metal.  <\/span><\/p>\n\n\n\n

Located between the elements gallium and thallium<\/a>, indium shares some chemical properties with these two substances. Namely, element 49 also has a low melting point and a property to wet glass. In its molten form, indium easily gets attached to glass and surfaces made of metal, quartz, ceramics, or marble.<\/span><\/p>\n\n\n\n

Indium reaches its boiling point at 2027\u00b0C (3681\u00b0F or 2300 K), while the melting point is achieved at 156.60\u00b0C (313.88\u00b0F or 429.75 K). It adopts a face-centered tetragonal structure and burns violently with a violet flame when exposed to temperatures above its melting point. <\/span><\/p>\n\n\n\n

Furthermore, this member of the aluminum family of elements in the periodic table has an electronegativity of 2 according to Pauling, whereas the atomic radius according to van der Waals is 0.162 nm. The electron shell of indium remains stable in air and in contact with H2O molecules, but it\u2019s easily dissolved through contact with acids.<\/span><\/p>\n\n\n\n

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

In 1863, the German chemists Ferdinand Reich (1799 \u2013 1882) and Hieronymous Theodor Richter (1824 \u2013 1898) were assigned to analyze a sample of mineral zinc<\/a> blende at the Freiberg University of Mining and Technology where they both were employed. The ore sample was sphalerite (ZnS) obtained from a location near Freiberg, Saxony. They suspected that the sample contained traces of the element thallium, which had been recently discovered at the time.<\/span><\/p>\n\n\n\n

During their scientific attempts, these two chemists first isolated the pyrite, arsenopyrite, galena, and sphalerite minerals from the ore. Next, they dissolved the minerals in hydrochloric acid and distilled raw zinc chloride, which resulted in a yellow precipitate. <\/span><\/p>\n\n\n\n

Believing they had produced thallium sulfide, Reich and Richter wanted to confirm their finding by analyzing the isolated product with the spectroscopy method. This brought them to the realization that the color line displayed after the procedure did <\/span>not <\/span><\/i>belong to the already known element thallium. Unlike the green of thallium, <\/span>this <\/span><\/i>color line was vibrantly violet and unseen before. This finding convinced them that a new chemical element is contained in the mineral ore. <\/span><\/p>\n\n\n\n

Hieronymous Theodor Richter continued to further inspect and analyze the new substance. His scientific efforts led him to eventually isolate the pure indium metal in 1864. Finally, an ingot of the new element was presented at the World Fair in 1867.<\/span><\/p>\n\n\n\n

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

As a result of the luminescent indigo line that can be seen in the indium’s spectrum, the name of element 49 was derived from the Latin word ‘<\/span>indicium<\/span><\/i>‘, which means \u201cof India\u201d. This is because historically, indigo-colored dye (close to violet) was produced in India and exported from there to the rest of the world.<\/span><\/p>\n\n\n\n

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

Indium is as rare as silver<\/a>, and in similar abundance to bismuth<\/a> and mercury<\/a>, so that it\u2019s rarely found in nature in its free elemental form. Typically, it occurs as a trace element in minerals. In the Universe, indium is formed through the slow neutron-capture process (or: the s-process) in stars of low and medium mass, as well as by the rapid neutron-capture process (or: the r-process). <\/span><\/p>\n\n\n\n

The sphalerite (a sulfidic zinc ore) is the main ore from which indium is obtained as a by-product for commercial uses after its separation from zinc. Polymetallic deposits from mineral ores, and also iron<\/a>, tin, and copper<\/a> ores are also great sources for mining indium. Geographically, zinc ore is most exploited for the extraction of the indium metal in China, Australia, the United States, Peru, and Canada.<\/span><\/p>\n\n\n\n

Until 1924, there was merely a gram of indium metal produced in the entire world. In recent years, the growing popularity of flat-panel LCD televisions and computer monitors and the necessity for indium in their production drastically increased the market demands and led to an annual production of <\/span>1000 tonnes<\/span><\/a> of this rare metal through mining. Plus, the recycling and manufacturing efficiency of indium provides an additional 650 tonnes of indium to the world\u2019s available resources of element 49.\u00a0<\/span><\/p>\n\n\n\n

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Indium in Everyday Life<\/span><\/h2>\n\n\n\n

The first notable use of larger amounts of indium is evidenced during World War II when this rare metal was used as a coating for the bearings of high-performance aircraft engines. Indium was used to prevent damage and corrosion of the planes that participated in the war. <\/span><\/p>\n\n\n\n

Both the chemical and the physical properties of indium make this element suitable for other versatile applications, mainly in manufacturing industries:<\/span><\/p>\n\n\n\n