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Indium,  49In
General properties
Name, symbol indium, In
Appearance silvery lustrous gray
Indium in the periodic table


Atomic number 49
Standard atomic weight 114.818(1)
Element category post-transition metal
Group, block group 13, p-block
Period period 5
Electron configuration [Kr] 4d10 5s2 5p1
per shell 2, 8, 18, 18, 3
Physical properties
Phase solid
Melting point 429.7485 K ​(156.5985 °C, ​313.8773 °F)
Boiling point 2345 K ​(2072 °C, ​3762 °F)
Density near r.t. 7.31 g·cm−3
liquid, at m.p. 7.02 g·cm−3
Triple point 429.7445 K, ​~1 kPa[1]
Heat of fusion 3.281 kJ·mol−1
Heat of vaporization 231.8 kJ·mol−1
Molar heat capacity 26.74 J·mol−1·K−1
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1196 1325 1485 1690 1962 2340
Atomic properties
Oxidation states 3, 2, 1 ​(an amphoteric oxide)
Electronegativity Pauling scale: 1.78
Ionization energies 1st: 558.3 kJ·mol−1
2nd: 1820.7 kJ·mol−1
3rd: 2704 kJ·mol−1
Atomic radius empirical: 167 pm
Covalent radius 142±5 pm
Van der Waals radius 193 pm
Crystal structure tetragonal
Tetragonal crystal structure for indium
Speed of sound thin rod, at 20 °C 1215 m·s−1
Thermal expansion 32.1 µm·m−1·K−1 (at 25 °C)
Thermal conductivity 81.8 W·m−1·K−1
Electrical resistivity at 20 °C: 83.7 nΩ·m
Magnetic ordering diamagnetic[2]
Young's modulus 11 GPa
Mohs hardness 1.2
Brinell hardness 8.83 MPa
CAS number 7440-74-6
Discovery Ferdinand Reich and Hieronymous Theodor Richter (1863)
First isolation Hieronymous Theodor Richter (1867)
Most stable isotopes
iso NA half-life DM DE (MeV) DP
113In 4.29% (SF) <24.281
115In 95.71% 4.41×1014 y β 0.495 115Sn
Decay modes in parentheses are predicted, but have not yet been observed

Indium is a chemical element with symbol In and atomic number 49. It is a post-transition metalic element that is rare in Earth's crust. It has no obvious role in biological processes, but is of considerable industrial importance. The metal is very soft, malleable and easily fusible, with a melting point higher than sodium, but lower than lithium or tin. Given its physical nature and position in the periodic table, it counts as a heavy metal, but in common circumstances is not a toxic hazard. Chemically, indium is similar to gallium and thallium, and it is largely intermediate between the two in terms of its properties.[3]


  • Characteristics 1
    • Physical 1.1
    • Chemical 1.2
    • Biological and medical 1.3
    • Isotopes 1.4
    • Creation 1.5
    • Occurrence 1.6
  • History 2
  • Production 3
  • Applications 4
    • Electronics 4.1
    • Metal and alloys 4.2
    • Other uses 4.3
  • Precautions and health issues 5
  • See also 6
  • References 7
  • External links 8



Indium wetting the glass surface of a test tube

Indium is a very soft, silvery-white, highly ductile, relatively rare post-transition metal with a bright luster.[4] It is so soft (Mohs hardness 1.2) that the metal can be cut with a knife, as can sodium. It also leaves a visible line on paper.[5] Like tin, when it is bent indium emits a high-pitched "cry".[4] Like gallium, indium is able to wet glass. Like both, indium has a low melting point, 156.60 °C (313.88 °F); higher than its lighter homologue, gallium, but lower than its heavier homologue, thallium, and lower than tin. Only mercury, gallium, and most of the alkali metals have lower melting points.[6] Its boiling point is, however, moderate, being 2072 °C (3762 °F), which is higher than that of thallium, but lower than that of gallium, showing opposition to the melting points trend. Indium thus has a very large liquid range of around 2000 °C. The density of indium, 7.31 g·cm−3, is also higher than that of gallium, but lower than that of thallium. Below its critical temperature of 3.41 K, indium becomes a superconductor. At standard temperature and pressure, indium crystallizes in the tetragonal crystal system in the space group I4/mmmm (lattice parametersa = 325 pm, c = 495 pm).[6]


Indium is an post-transition metal and chemically, is the intermediate element between its group 13 neighbors gallium and thallium. An indium atom has 49 electrons, having an electronic configuration of [Kr]4d105s25p1. In its compounds, indium most commonly loses its three outermost electrons, becoming indium(III) ions, In3+, but in some cases the pair of 5s-electrons can stay within the atom, indium thus being oxidized only to indium(I), In+. This happens due to the inert pair effect, which occurs because of the stabilization of 5s-orbital due to relativistic effects, which are stronger closer to the bottom of the periodic table. In(III) is the more stable oxidation state. Thallium (indium's heavier homolog) shows an even stronger effect, making oxidation to thallium(I) more likely than to thallium(III), making +1 the more likely oxidation state,[7] whereas gallium (indium's lighter homolog) commonly shows only the +3 oxidation state. Thus, although thallium(III) is a moderately strong oxidizing agent, indium(III) is stable and indium(I) is a powerful reducing agent.[8]

A number of standard electrode potentials, depending on the reaction under study,[9] are reported for indium:
−0.40 In2+ + e ↔ In+
−0.49 In3+ + e ↔ In2+
−0.443 In3+ + 2 e ↔ In+
−0.3382 In3+ + 3 e ↔ In
−0.14 In+ + e ↔ In

Indium does not react with water, but it is oxidized by stronger oxidizing agents, such as halogens or oxalic acid, to give indium(III) compounds. It does not react with boron, silicon or carbon, and the corresponding boride, silicide or carbide are not known. Similarly, reaction between indium and hydrogen has not been observed, but both indium(I) and indium(III) hydrides are known.[10]

Indium(III) oxide is formed at high temperatures during reaction between indium and oxygen, with blue flame. It is amphoteric, i. e. it can react with both acids and bases. Its reaction with water results in insoluble indium(III) hydroxide, which is also amphoteric, reacting with alkalies to give indates(III) and with acids to give indium(III) salts:

In(OH)3 + 2 NaOH → 2 Na[InO2] + H2O
In(OH)3 + 3 HCl → InCl3 + 3 H2O

The hydrolysis of sodium indate(III) gives weak indic acid, HInO2. Out of common indium(III) salts, chloride, sulfate and nitrate are soluble. In water solutions, In3+ and [InO2]- ions are hydrolyzed to give InOH2+ and HInO2 due to generally amphoteric character of indium(III) ions. Indium(III) compounds are not well-soluble, similarly to thallium(III) compounds; however, indium(III) salts of strong acids, such as chloride, sulfate and nitrate are soluble, hydrolyzing in water solutions. The In3+ ion is colorless in solution because of the absence of unpaired electrons in the d- and f-electron shells.[8]

Indium(I) compounds are not as common as indium(III) ones; only chloride,

  • Indium at The Periodic Table of Videos (University of Nottingham)
  • Reducing Agents > Indium low valent
  • NIOSH Pocket Guide to Chemical Hazards (Centers for Disease Control and Prevention)

External links

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  2. ^ Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press.  
  3. ^ W. M. Haynes, Ph.D.; David R. (ed.). Lide (2010). CRC Handbook of Chemistry and Physics: A Ready-reference Book of Chemical and Physical Data. CRC Press.  
  4. ^ a b c d Alfantazi, A. M.; Moskalyk, R. R. (2003). "Processing of indium: a review". Minerals Engineering 16 (8): 687–694.  
  5. ^ Binder, Harry H. (1999). Lexicon der chemischen Elemente (in Deutsch). S. Hirzel Verlag.  
  6. ^ a b Dean, John A. (523). Lange's handbook of chemistry (Fifteenth edition). McGraw-Hill, Inc.  
  7. ^ Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1985). "Thallium". Lehrbuch der Anorganischen Chemie (in Deutsch) (91–100 ed.). Walter de Gruyter. pp. 892–893.  
  8. ^ a b Bleshinsky, S. V.; Abramova, V. F. (1958). Химия индия (in Русский). Frunze. p. 252. 
  9. ^ Haynes, William M., ed. (2011).  
  10. ^ Bleshinsky, S. V.; Abramova, V. F. (1958). Химия индия (in Русский). Frunze. p. 301. 
  11. ^ Fischer, E. O.; Hofmann, H. P. (1957). "Metall-cyclopentadienyle des Indiums". Angewandte Chemie (in German) 69 (20): 639–640.  
  12. ^ a b Sinclair, Ian; Worrall, Ian J. (1982). "Neutral complexes of the indium dihalides". Canadian Journal of Chemistry 60 (6): 695–698.  
  13. ^ Beck, Horst Philipp; Wilhelm, Doris (1991). "In7Cl9—A New"Old" Compound in the System In-Cl". Angewandte Chemie International Edition in English 30 (7): 824–825.  
  14. ^ Dronskowski, Richard (1995). "Synthesis, Structure, and Decay of In4Br7". Angewandte Chemie International Edition in English 34 (10): 1126–1128.  
  15. ^ Audi, Georges; Bersillon, O.; Blachot, J.; Wapstra, A.H. (2003). "The NUBASE Evaluation of Nuclear and Decay Properties". Nuclear Physics A (Atomic Mass Data Center) 729: 3–128.  
  16. ^ Boothroyd, A. I. (2006). "Heavy elements in stars". Science 314 (5806): 1690–1691.  
  17. ^ "Abundance in Earth's Crust". Archived from the original on 9 March 2007. Retrieved 2007-04-14. 
  18. ^ Sutherland, J. K. (1971). "A second occurrence of dzhalindite". The Canadian Mineralogist 10 (5): 781–786. 
  19. ^ "Mineral Commodities Summary 2007: Indium" (PDF). United States Geological Survey. Retrieved 2007-12-26. 
  20. ^ a b "Indium and Gallium Supply Sustainability September 2007 Update" (PDF). 22nd EU PV Conference, Milan, Italy. Retrieved 2007-12-26. 
  21. ^ "Indium Price Supported by LCD Demand and New Uses for the Metal". September 6, 2009. 
  22. ^ "Top World Silver Producers" (PDF). World Silver Survey 2007. 
  23. ^ Reich, F.; Richter, T. (1863). "Ueber das Indium". Journal für Praktische Chemie (in German) 90 (1): 172–176.  
  24. ^ Venetskii, S. (1971). "Indium". Metallurgist 15 (2): 148–150.  
  25. ^ Reich, F.; Richter, T. (1864). "Ueber das Indium". Journal für Praktische Chemie (in German) 92 (1): 480–485.  
  26. ^ a b Schwarz-Schampera, Ulrich; Herzig, Peter M. (2002). Indium: Geology, Mineralogy, and Economics. Springer.  
  27. ^ French, Sidney J. (1934). "A story of indium". Journal of Chemical Education 11 (5): 270.  
  28. ^ Schwarz-Schampera, Ulrich; Herzig, Peter M; Rohstoffe, Bundesanstalt für Geowissenschaften und (2002-06-10). "history". Indium: Geology, mineralogy, and economics. p. 1.  
  29. ^ Weeks, R.A. (1973). "Gallium, germanium, and indium". In Brobst, Donald Albert; Pratt, Walden P. Mines and mineral resources. pp. 237–246. 
  30. ^ Jorgenson, John D.; George, Micheal W. "Mineral Commodity Profile Indium". United States Geological Survey. 
  31. ^ "Canadian Minerals Yearbook". 2007. Archived from the original on 2011-09-27. 
  32. ^ "Recycling Rates of Metals: A Status Report". United Nations Environmental Programme. Retrieved August 2, 2011. 
  33. ^ Fathi Habashi (21 November 2008). Alloys: Preparation, Properties, Applications. John Wiley & Sons. pp. 294–.  
  34. ^ U.S. Geological Survey - Historical Statistics for Mineral and Material Commodities in the United States; INDIUM STATISTICS // USGS, April 1, 2014
  35. ^ Tolcin, Amy C. (2013) Indium. USGS Mineral Commodity Summaries.
  36. ^ "Malku Khota Updated Preliminary Economic Assessment, May 2011". South American Silver Corp. Archived from the original on 2012-01-19. 
  37. ^ Wright, Philip (1996). "Mineral and Metal Commodity Review: Tin". Natural Resources Canada. Retrieved 2011-06-01. 
  38. ^ "Indium Price Supported by LCD Demand and New Uses for the Metal" (PDF). Retrieved 2007-12-26. 
  39. ^ "USGS Mineral Commodity Summaries 2011". USGS and USDI. Retrieved August 2, 2011. 
  40. ^ "How much is left?". ScientificAmerican. Retrieved 16 January 2013. 
  41. ^ Tolcin, Amy C. "Mineral Yearbook 2007: Indium" (PDF). United States Geological Survey. Retrieved 200-02-03. 
  42. ^ a b Downs, Anthony John (1993). Chemistry of Aluminium, Gallium, Indium, and Thallium. Springer. pp. 89 and 106.  
  43. ^ "The Electroluminescent Light Sabre". Nanotechnology News Archive. Azonano. June 2, 2005. Retrieved 2007-08-29. 
  44. ^ Bachmann, K. J. (1981). "Properties, Preparation, and Device Applications of Indium Phosphide". Annual Review of Materials Science 11: 441–484.  
  45. ^ Bhuiyan, Ghani; Hashimoto, Akihiro; Yamamoto, Akioare (2003). "Indium nitride (InN): A review on growth, characterization, and properties". Journal of Applied Physics 94 (5): 2779.  
  46. ^ Powalla, M.; Dimmler, B. (2000). "Scaling up issues of CIGS solar cells". Thin Solid Films. 361–362: 540–546.  
  47. ^ Schubert, E. Fred (2003). Light-Emitting Diodes. Cambridge University Press. p. 16.  
  48. ^ Shenai, Deodatta V.; Timmons, Michael L.; DiCarlo Jr., Ronald L.; Marsman, Charles J. (2004). "Correlation of film properties and reduced impurity concentrations in sources for III/V-MOVPE using high-purity trimethylindium and tertiarybutylphosphine". Journal of Crystal Growth 272 (1–4): 603–608.  
  49. ^ Geological Survey (U.S.) (2010). Minerals Yearbook, 2008, V. 1, Metals and Minerals. Government Printing Office. pp. 35–2.  
  50. ^ Rabilloud, Guy (1997). High-performance Polymers: Conductive adhesives. Editions TECHNIP. p. 263.  
  51. ^ Weissler, G. L., ed. (1990). "Vacuum physics and technology". San Diego: Acad. Press. p. 296. ISBN . 
  52. ^ Reading, Mike; Hourston, Douglas J. (2006). Modulated temperature differential scanning calorimetry. Springer. p. 245.  
  53. ^ Surmann, P; Zeyat, H (Nov 2005). "Voltammetric analysis using a self-renewable non-mercury electrode". Analytical and Bioanalytical Chemistry 383 (6): 1009–13.  
  54. ^ Weber, Dieter. "Bonding ceramic sputter targets to metal holders". Retrieved 19 October 2014. 
  55. ^ Preston-Thomas, H. (1990). "Procès-Verbaux du Comité International des Poids et Mesures". Metrologia 27 (1): 3–10.  
  56. ^ Scoullos, Michael J (2001-12-31). "Other types of cadmium alloys". Mercury, cadmium, lead: handbook for sustainable heavy metals policy and regulation. p. 222.  
  57. ^ Berger, Harold; National Bureau Of Standards, United States; Committee E-7 On Nondestructive Testing, American Society for Testing and Materials (1976). "Image Detectors for Other Neutron Energies". Practical applications of neutron radiography and gaging: a symposium. pp. 50–51. 
  58. ^ Tong, Xingcun Colin (2011). Advanced Materials for Thermal Management of Electronic Packaging. Springer. p. 323.  
  59. ^ Van Nostrand, D.; Abreu, S. H.; Callaghan, J. J.; Atkins, F. B.; Stoops, H. C.; Savory, C. G. (May 1988). "In-111-labeled white blood cell uptake in noninfected closed fracture in humans: prospective study". Radiology (Radiological Society of North America, Inc.) 167 (2): 495–498.  
  60. ^ Felix, Noël "Indium and Indium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2000, Wiley-VCH, Weinheim. doi:10.1002/14356007.a14_157.


See also

No authoritative evidence has been reported for health hazards associated with the use of indium.[60]

Precautions and health issues

  • Indium tin oxide is used as a light filter in low-pressure sodium vapor lamps. The infrared radiation is reflected back into the lamp, which increases the temperature within the tube and therefore improves the performance of the lamp.[42]
  • Indium's melting point of 429.7485 K (156.5985 °C) is a defining fixed point on the international temperature scale ITS-90.[55]
  • Indium's high neutron capture cross section for thermal neutrons makes it suitable for use in control rods for nuclear reactors, typically in an alloy containing 80% silver, 15% indium, and 5% cadmium.[56]
  • In nuclear engineering, the (n,n') reactions of 113In and 115In are used to determine magnitudes of neutron fluxes.[57]
  • Indium is also used as a thermal interface material by personal computer enthusiasts in the form of pre-shaped foil sheets fitted between the heat-transfer surface of a microprocessor and its heat sink. The application of heat partially melts the foil and allows the indium metal to fill in any microscopic gaps and pits between the two surfaces, removing any insulating air pockets that would otherwise compromise heat transfer efficiency.[58]
  • 111In emits gamma radiation and is used in indium leukocyte imaging, or indium scintigraphy, a technique of medical imaging that is particularly helpful in differentiating conditions such as osteomyelitis from decubitus ulcers for assessment of route and duration of antibiotic therapy.[59] Indium leukocyte scintigraphy has many applications, including early phase drug development, and the monitoring of activity of white blood cells. For the test, blood is taken from the patient, white cells removed, labeled with the radioactive 111In, then re-injected back into the patient. Gamma imaging will then reveal any areas of on-going white-cell localization such as new and developing areas of infection.

Other uses

  • Very small amounts used in aluminium alloy sacrificial anodes (for salt water applications) to prevent passivation of the aluminium.
  • To bond gold electrical test leads to superconductors, indium is used as a conducting adhesive and applied under a microscope with precision tweezers.[50]
  • In the form of a wire it is used as a vacuum seal and a thermal conductor in cryogenics and ultra-high-vacuum applications, for example, in manufacturing gaskets that deform to fill gaps.[51]
  • Used as a calibration material for Differential scanning calorimetry.[52]
  • It is an ingredient in the gallium–indium–tin alloy galinstan, which is liquid at room temperature but not toxic like mercury.[53]
  • Indium soldering is the preferred method to create a stress-free electrically and thermally conducting bond between a ceramic sputter target and a target holder. [54]
Ductile indium wire

Metal and alloys


The first large-scale application for indium was as a coating for bearings in high-performance aircraft engines during World War II. Afterward, production gradually increased as new uses were found in fusible alloys, solders, and electronics. In the 1950s, tiny beads of it were used for the emitters and collectors of PNP alloy junction transistors. In the middle and late 1980s, the development of indium phosphide semiconductors and indium tin oxide thin films for liquid crystal displays (LCD) aroused much interest. By 1992, the thin-film application had become the largest end use.[41][42]

A magnified image of an LCD screen showing RGB pixels. Individual transistors are seen as white dots in the bottom part.


It has been estimated that there are fewer than 14 years left of indium supplies, based on current rates of extraction, demonstrating the need for additional recycling.[40]

The amount of indium consumed is largely a function of worldwide LCD production. Worldwide production in 2007 was 475 tonnes per year from mining and a further 650 tonnes per year from recycling.[20] Demand has risen rapidly in recent years with the popularity of LCD computer monitors and television sets, which now account for 50% of indium consumption.[38] Increased manufacturing efficiency and recycling (especially in Japan) maintain a balance between demand and supply. According to the UNEP, indium's end-of-life recycling rate is less than 1%.[39] Demand increased as the metal is used in LCDs and televisions, and supply decreased when a number of Chinese mining concerns stopped extracting indium from their zinc tailings. In 2002, the price was US$94 per kilogram. The recent changes in demand and supply have resulted in high and fluctuating prices of indium, which from 2006 to 2009 ranged from US$382/kg to US$918/kg.

Indium is produced mainly from residues generated during zinc ore processing but is also found in iron, lead, and copper ores.[4] China is a leading producer of indium (390 tonnes in 2012), followed by Canada, Japan and South Korea with 70 tonnes each.[35] The Teck Cominco refinery in Trail, British Columbia, is a large single-source indium producer, with an output of 32.5 tonnes in 2005, 41.8 tonnes in 2004 and 36.1 tonnes in 2003. South American Silver Corporation's Malku Khota property in Bolivia is a large resource of indium with an indicated resource of 1,481 tonnes and inferred resource of 935 tonnes.[36] Adex Mining Inc.’s Mount Pleasant Mine in New Brunswick, Canada, holds some of the world’s total known indium resources.[37]

The lack of indium mineral deposits and the fact that indium is enriched in sulfidic lead, tin, copper, iron and predominately in zinc deposits, makes zinc production the main source for indium. The indium is leached from slag and dust of zinc production. Further purification is done by electrolysis. The exact process varies with the exact composition of the slag and dust.[4][26]

World production trend[34]


Currently the demand for indium is driven by the manufacture of transparent electrodes from indium tin oxide (ITO). The electrodes are used in liquid crystal displays and touchscreens. The metal also is used in a wide range of alloys;[33] one of its first large-volume applications was in high-performance bearing alloys for aircraft) in WWII. It is also used for making particularly low melting point alloys, and is a component in some solders. One of its unusual attributes is that, like gallium molten indium wets glass, so that it can be used as a solder in glass seals. It also is used in a wide range of electric and electronic roles, and has been used in superconducting alloys.

In 1924, indium was found to have a valued ability to stabilize non-ferrous metals, which was the first significant use for the element.[27] It took until 1936 for the U.S. Bureau of Mines to list indium as a commodity, and even in the early 1950s only very limited applications for indium were known, the most important of which was making light-emitting diodes and coating bearings for aircraft engines during World War II. The start of production of indium-containing semiconductors started in 1952. The development and widespread use of indium-containing nuclear control rods increased demand during the 1970s, and the use of indium tin oxide in liquid crystal displays increased and became the major application by 1992.[28][29][30][31][32]

Richter went on to isolate the metal in 1864.[25] At the World Fair 1867 an ingot of 0.5 kg (1.1 lb) was presented.[26]

In 1863, the German chemists Ferdinand Reich and Hieronymous Theodor Richter were testing ores from the mines around Freiberg, Saxony. They dissolved the minerals pyrite, arsenopyrite, galena and sphalerite in hydrochloric acid and distilled raw zinc chloride. As it was known that ores from that region sometimes contain thallium they searched for the green emission lines with spectroscopy. The green lines were absent but a blue line was present in the spectrum. As no element was known with a bright blue emission they concluded that a new element was present in the minerals. They named the element with the blue spectral line indium, from the indigo color seen in its spectrum.[23][24] That line was the first indication of an unknown element in zinc ores, and when the free metal was isolated in the following year it was named indium after the colour of the light that had provided a clue to its presence. Zinc ores still are the primary source of indium


Based on content of indium in zinc ore stocks, there is a worldwide reserve of approximately 6,000 tonnes of economically viable indium.[19] However, the Indium Corporation, the largest processor of indium, claims that, on the basis of increasing recovery yields during extraction, recovery from a wider range of base metals (including tin, copper and other polymetallic deposits) and new mining investments, the long-term supply of indium is sustainable, reliable, and sufficient to meet increasing future demands.[20] This conclusion may be reasonable considering that silver, which is one-third as abundant as indium in Earth's crust,[21] is currently mined at approximately 18,300 tonnes per year,[22] which is 40 times greater than current indium mining rates.

In Earth's crust, indium occurs only in the form of its compounds, except occasionally as rare grains of free metal of no commercial importance. Indium is 68th most abundant element in Earth's crust at approximately 160 ppb, making indium approximately as abundant as cadmium.[17] Fewer than 10 indium minerals are known, such as dzhalindite (In(OH)3) and indite (FeIn2S4),[18] but none of these occurs in significant deposits.


Indium is created via the long-lasting, (up to thousands of years), s-process in low-to-medium mass stars (which range in mass between 0.6 and 10 solar masses). When a silver-109 atom (the isotope of which approximately half of all silver in existence is composed), catches a neutron, it undergoes a beta decay to become cadmium-110. Capturing further neutrons, it becomes cadmium-115, which decays to indium-115 via another beta decay. This explains why the radioactive isotope predominates in abundance compared to the stable one.[16]

yellow squares with red and blue arrows
The s-process acting in the range from silver to antimony.


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; these are the only naturally occurring isotopes. The most stable artificial indium isotope is indium-111, which has half-life of approximately 2.8 days. All other isotopes have half-lives shorter than 5 hours. Indium also has 47 meta states, out of which indium-114m1 is the most stable, being more stable than the ground state of any indium isotope (except for the primordial ones).

Indium occurs naturally on Earth only in two primordial nuclides, indium-113 and indium-115. Indium-115 makes up 95.7% of all indium but it is radioactive, decaying to tin-115 via beta decay with half-life of 4.41×1014 years, four orders of magnitude longer than the age of the universe and nearly 50,000 times longer than that of natural thorium.[15] This situation is uncommon among stable chemical elements; only indium, tellurium, and rhenium have been shown to have most-abundant isotopes that are radioactive. The less common natural isotope of indium, indium-113, is stable.


Indium is not known to have any nuclear medicine tests, as a radiotracer to follow the movement of labeled proteins and white blood cells in the body.

Biological and medical

Less frequently, indium shows an intermediate oxidation state +2, in compounds with an In–In bond, most notably in indium-mediated allylation.

. cyclopentadienyl complexes is polymer consisting of zigzag chains of alternating indium atoms and [11]

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