Indium is characterized as post transition metal. It was discovered it 1863 and have found wide use in making semiconductors and transistors. Indium has no biological role but is toxic when inhaled or ingested.
Discovery and History
In 1863, Hieronymous Richter and Ferdinand Reich discovered indium by spectroscopic methods. The name indium was given to the novel element for its indigo blue line in its spectrum. Its symbol is In. Pure indium was isolated in 1864 [1]. In its early days, indium was used as a coating agent of bearing of aircraft engines in World War II. In 1950, indium beads were used in junction transistors.
Indium
| Periodic Table Classification | Group 13 Period 5 |
|---|---|
| State at 20C | Solid |
| Color | Silvery lustrous gray |
| Electron Configuration | [Kr] 4d10 5s2 5p1 |
| Electron Number | 49 |
| Proton Number | 49 |
| Electron Shell | 2, 8, 18, 18, 3 |
| Density | 7.31 g.cm-3 at 20°C |
| Atomic number | 49 |
| Atomic Mass | 114.82 g.mol -1 |
| Electronegativity according to Pauling | 1.78 |
Occurrence
Indium is present in Earth’s crust in around 0.21 ppm. It is not present in elemental or free form. Indium does not have any ore that contain high concentration of this metal. Naturally, it is present in little amounts with ores of copper, lead, iron and zinc. Commercially, indium is obtained as a byproduct during the refining of zinc sulfide ores. The largest producer of indium is China, followed by Canada, Japan and South Korea [2].
Physical Characteristics
Indium is a silver white lustrous metal. It is soft and can be cut with a knife. Indium has a low melting point (156.60 C) and boiling point is 2072 C. The density of indium is 7.31 g/cm3. Indium has the ability to become a superconductor below the critical temperature. Indium is resistant to corrosion.
Chemical Characteristics
Indium is not very reactive metal. it does not form compounds with water. Reaction of halogens with indium lead to the production of indium (III) compounds. Indium does not react with base and is insoluble in alkaline solutions. When burned in air, indium (III) forms indium oxide, which can react with both acids and base (an amphoteric compound). The most common oxidation state of indium is +2.
Significance and Uses
- Indium is widely used in the semiconductor industry. It is used in the manufacturing of LCD screens for television and computer monitors. This accounts for around half of the worldwide usage of indium [4].
- indium oxides are used as conductive coating on glass in electroluminescent panels.
- Indium is used in the manufacturing of ultra-high-vacuum applications, such as various electron and X-rays electro-photon spectroscopy.
- It is used in cryogenic applications for the study and production of various materials at low temperature.
- Indium is used in amalgam alloys used for dental purposes.
- It is used as control rod in nuclear reactors.
- Radioactive isotope of indium (indium-111) is used in nuclear medicine studies for the movement of blood cells in the body.
Health Hazards
Indium (III) is toxic to the body if ingested. It damages the kidneys and is more toxic in aqueous solution as compared to direct injection of metal into the body [5]. Indium toxicity is mostly an occupational hazard and personals can develop symptoms of toxicity through ingestion, eye contact, inhalation and contact with skin.
Isotopes of Indium
Indium has thirty-nine isotopes, which range in mass number from 97 to 135. There are only two naturally occurring isotopes, indium-113 and indium-115. The only stable isotope is indium-113. And indium-115 is the most abundant isotope. Among the artificial isotopes, indium-111 is the most stable with half life of 2.8 days. All indium isomers undergo decay via isomeric transition [6].
REFERENCES
[1]. J.W. Mellor, A Comprehensive Treatise on Inorganic and Theoretical Chemistry., 1929, vol v, Longmans, Green and Co., p 387,388
[2]. Indium – in: USGS Mineral Commodity Summaries (PDF). United States Geological Survey. 2017.
[3]. “Indium Price Supported by LCD Demand and New Uses for the Metal”. Geology.com. Archived from the original (PDF) on 2007-12-21. Retrieved 2007-12-26.
[4] “Indium Price Supported by LCD Demand and New Uses for the Metal”. Geology.com. Archived from the original (PDF) on 2007-12-21. Retrieved 2007-12-26.
[5]. Castronovo, F. P.; Wagner, H. N. (October 1971). “Factors Affecting the Toxicity of the Element Indium”. British Journal of Experimental Pathology. 52 (5): 543–559. PMC 2072430. PMID 5125268.
[6]. Audi, Georges; Bersillon, O.; Blachot, J.; Wapstra, A. H. (2003). “The NUBASE Evaluation of Nuclear and Decay Properties”. Nuclear Physics A. 729 (1): 3–128. Bibcode:2003NuPhA.729….3A. CiteSeerX 10.1.1.692.8504. doi:10.1016/j.nuclphysa.2003.11.001.