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Name, Symbol, NumberIndium, In, 49
Chemical series True metals[?]
Group, Period, Block13 (IIIA)[?], 5 , p
Density, Hardness 7310 kg/m3, 1.2
Appearance silvery lustrous gray
Atomic Properties
Atomic weight 114.818 amu
Atomic radius (calc.) 155 (156) pm
Covalent radius 144 pm
van der Waals radius 193 pm
Electron configuration [Kr]4d10 5s2 5p1
e- 's per energy level2, 8, 18, 18, 3
Oxidation states (Oxide) 3 (amphoteric)
Crystal structure Tetragonal
Physical Properties
State of matter solid
Melting point 429.75 K (313.88 F)
Boiling point 2345 K (3762 F)
Molar volume 15.76 ×10-3 m3/mol
Heat of vaporization 231.5 kJ/mol
Heat of fusion 3.263 kJ/mol
Vapor pressure 1.42 E-17 Pa at 429 K
Speed of sound 1215 m/s at 293.15 K
Electronegativity 1.78 (Pauling scale)
Specific heat capacity 233 J/(kg*K)
Electrical conductivity 11.6 106/m ohm
Thermal conductivity 81.6 W/(m*K)
1st ionization potential 558.3 kJ/mol
2nd ionization potential 1820.7 kJ/mol
3rd ionization potential 2704 kJ/mol
4th ionization potential 5210 kJ/mol
Most Stable Isotopes
isoNAhalf-life DMDE MeVDP
113In4.3%In is stable with 64 neutrons
115In95.7%4.41 E14 yBeta-0.495115Sn
SI units & STP are used except where noted.
Indium is a chemical element in the periodic table that has the symbol In and atomic number 49. This rare, soft, malleable and easily fusible true metal[?], is chemically similar to aluminum or gallium but looks more like zinc (zinc ores are also the primary source of this metal). Its current primary application is to form thin-films for use as lubricated layers (during WWII it was widely used to coat bearings in high-performance aircraft).

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Notable Characteristics Indium is a very soft, silvery-white true metal[?] that has a bright luster. As a pure metal indium emits a high-pitched "cry" when it is bent. Both gallium and indium are able to wet glass. Applications The first large-scale application for indium was as a coating for bearings in high-performance aircraft engines during World War II. Afterwards, production gradually increased as new uses were found in fusible alloys, solders, and electronics. 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. Other uses;

History Indium (named after the indigo line in its atomic spectrum[?]) was discovered by Ferdinand Reich[?] and Theodore Richter[?] in 1863 while they were testing zinc ores with a spectrograph in search of thallium. Richter went on to isolate the metal in 1867. Occurrence Indium is produced mainly from residues generated during zinc ore processing but is also found in iron, lead, and copper ores. The amount of indium consumed is largely a function of worldwide LCD production. Increased manufacturing efficiency and recycling (especially in Japan) maintain a balance between demand and supply. The average indium price for 2000 was US$188 per kilogram.

Up until 1924, there was only about a gram of isolated indium on the planet. The Earth is estimated to contain abou 0.1 ppm of indium which means it is about as abundant as silver. Canada is a leading producer of indium, producing more than 1,000,000 troy ounces in 1997. Precautions There is some unconfirmed evidence that suggests that indium has a low level of toxicity. However in the welding and semiconductor industries, where indium exposure is relatively high, there have been no reports of any toxic side-effects.

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