Indium is a chemical element with atomic number 49. It is represented by the symbol In. Indium is a rare and soft metal. Chemically, it resembles gallium and thallium. Indium was discovered in Zinc ores by Ferdinand Reich and Hieronymous T. Richter in 1983. The element was named after the brilliant indigo line in its spectrum. The presence of blue lines in the zinc ores was clearly indicated the presence of an unknown element which was later discovered and named indium. Zinc ores are the primary source of indium, where it is found in compound form. It is rarely found as free metal.
In the year 1863, German chemists Ferdinand Reich and Hieronymous T. Richter were testing ores from the mines around Freiberg in Germany. Thallium was abundantly found in the region. Hence they searched for green emission lines with spectroscopic methods. But emission lines were found to be blue instead of green. As no element was known with a bright blue emission they concluded the presence of a new element in the minerals. In 1924, indium was used to stabilize nonferrous metals. During World War-II, indium was used to manufacture aircraft engines and light emitting diodes. The demand and widespread use of indium increased during the 1970s.
Indium is a soft, silver-white and a rare metal with a bright luster.
It has a low melting point of 156.60 °C (313.88 °F) that is higher than gallium and lower than thallium.
The boiling point of Indium is moderate, being 2072 °C (3762 °F), which is higher than that of thallium, but lower than that of gallium, showing opposition to melting points trend.
In its purest form, this metallic element is non-toxic.
Indium shows two main oxidation states, which are +1 and +3, with latter being more stable. Indium(I) is a powerful reducing agent ( donates an electron to another molecules or atom group).
Indium is easily oxidized by stronger oxidizing agents, such as halogens or oxalic acid.
Indium does not react with water, born, silicon or carbon.
Indium has 39 known isotopes, ranging in mass between 97 and 135. Only one of them is stable and one has half-life exceeding 1014 years. The other most stable indium isotope is indium-111, which has half-life of approximately 2.8 days. All other isotopes have half-lives less than 5 hours.
Indium has unique electrical and optical properties. Indium compounds such as indium antimonide, indium phosphide, and indium nitride are used as semiconductors.
Indium is used to manufacture CIGS (copper indium gallium selenide) semiconductor. It is made into thin film solar cells.
It is used in the production of low melting alloys along with gallium.Indium can be coated on metals and evaporated onto glass, to form mirrors equal to that made with silver and more corrosion resistant. Thin films of indium-tin oxide are used for liquid crystal displays (LCDs).
Indium has its application even in nuclear engineering.