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Indium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


                49                 cadmium ← indium → tin
                Ga
                ↑
                In
                ↓
                Tl

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                       Name, Symbol, Number indium, In, 49
                                               Chemical series poor metals
                                             Group, Period, Block 13, 5, p
                                          Appearance silvery lustrous gray
                                             Atomic mass 114.818 (3) g/mol
                               Electron configuration [Kr] 4d^10 5s^2 5p^1
                                       Electrons per shell 2, 8, 18, 18, 3
                                                       Physical properties
                                                               Phase solid
                                       Density (near r.t.) 7.31 g·cm^−3
                                    Liquid density at m.p. 7.02 g·cm^−3
                                                   Melting point 429.75  K
                                                (156.60 ° C, 313.88 ° F)
                                                      Boiling point 2345 K
                                                    (2072 ° C, 3762 ° F)
                                         Heat of fusion 3.281 kJ·mol^−1
                                   Heat of vaporization 231.8 kJ·mol^−1
                          Heat capacity (25 °C) 26.74 J·mol^−1·K^−1

   CAPTION: Vapor pressure

                                      P/Pa   1    10  100  1 k  10 k 100 k
                                     at T/K 1196 1325 1485 1690 1962 2340

                                                         Atomic properties
                                              Crystal structure tetragonal
                                                        Oxidation states 3
                                                       ( amphoteric oxide)
                                    Electronegativity 1.78 (Pauling scale)
                                                       Ionization energies
                                           ( more) 1st: 558.3 kJ·mol^−1
                                                  2nd: 1820.7 kJ·mol^−1
                                                    3rd: 2704 kJ·mol^−1
                                                      Atomic radius 155 pm
                                              Atomic radius (calc.) 156 pm
                                                    Covalent radius 144 pm
                                               Van der Waals radius 193 pm
                                                             Miscellaneous
                                                 Magnetic ordering no data
                               Electrical resistivity (20 °C) 83.7 nΩ·m
                       Thermal conductivity (300 K) 81.8 W·m^−1·K^−1
                       Thermal expansion (25 °C) 32.1 µm·m^−1·K^−1
                               Speed of sound (thin rod) (20 °C) 1215 m/s
                                                    Young's modulus 11 GPa
                                                         Mohs hardness 1.2
                                                 Brinell hardness 8.83 MPa
                                             CAS registry number 7440-74-6
                                                         Selected isotopes

                  CAPTION: Main article: Isotopes of indium

                          iso    NA    half-life     DM   DE ( MeV)   DP
                         ^113In 4.3%  In is stable with 64 neutrons
                         ^115In 95.7% 4.41×10^14 y Beta^- 0.495     ^115Sn

                                                                References

   Indium ( IPA: /ˈɪndiəm/) is a chemical element in the periodic table
   that has the symbol In and atomic number 49. This rare, soft, malleable
   and easily fusible poor metal, is chemically similar to aluminium or
   gallium but looks more like zinc (zinc ores are also the primary source
   of this metal). Its current primary application is to form transparent
   electrodes from Indium tin oxide in liquid crystal displays. It is also
   widely used in thin-films to form lubricated layers (during World War
   II it was widely used to coat bearings in high-performance aircraft).

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.

   One unusual property of indium is that its most common isotope is very
   slightly radioactive; it very slowly decays by beta emission to tin
   over time. This radioactivity is not considered hazardous, mainly
   because its decay rate is nearly 50,000 times slower than that of
   natural thorium, with a half-life of 4×10^14 years. Also, indium is not
   a notorious cumulative poison, like its neighbour cadmium, and is
   relatively rare.

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;
     * Used in the manufacture of low-melting-temperature alloys. An alloy
       consisting of 24% indium and 76% gallium is liquid at room
       temperature.
     * Some indium compounds such as indium antimonide, indium phosphide,
       and indium nitride are semiconductors with useful properties.
     * Used in Light Emitting Diodes (LED's) and Laser Diodes (LD's) based
       on compound semiconductors that are fabricated by Metalorganic
       Vapor Phase Epitaxy ( MOVPE) technology.
     * The ultrapure metalorganics of indium, specifically high purity
       trimethylindium (TMI) is used as a precursor in III-V compound
       semiconductors, while it is also used as the semiconductor dopant
       in II-VI compound semiconductors.
     * Can also be plated onto metals and evaporated onto glass which
       forms a mirror which is as good as those made with silver but has
       higher corrosion resistance.
     * Its oxide is used in the making of electroluminescent panels.
     * Used as a light filter in Low pressure sodium vapor lamps
     * Indium's freezing point of 429.7485 K (156.5985 °C) is a defining
       fixed point on the international temperature scale ITS-90.
     * Sometimes used as a component of nuclear control rods.
     * Very small amounts used in aluminium alloy sacrificial anodes (for
       salt water applications) to prevent passivation of the aluminium

History

   Indium (named after the indigo line in its atomic spectrum) was
   discovered by Ferdinand Reich and Hieronymous Theodor Richter in 1863
   while they were testing zinc ores with a spectrograph in search of
   thallium. It is interesting to note that most elements were discovered
   while searching for other elements. Richter went on to isolate the
   metal in 1867.

Occurrence

   Ductile Indium wire
   Enlarge
   Ductile Indium wire

   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 2005 was US$900 per kilogram. This is unusually high. 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/Kg.

   Up until 1924, there was only about a gram of isolated indium on the
   planet. The Earth is estimated to contain about 0.1 ppm of indium which
   means it is about as abundant as silver, although indium is in fact
   nearly three times more expensive by weight. Canada is a leading
   producer of indium. The TeckCominco refinery in Trail, BC, is the
   largest single source, with production of 32,500 kg in 2005, 41,800 kg
   in 2004 and 36,100 kg in 2003. Worldwide production is typically over
   300 tonnes per year, but demand has risen rapidly with the increased
   popularity of LCD computer monitors and televisions.

Precautions

   Pure indium in metal form is considered non-toxic by most sources. In
   the welding and semiconductor industries, where indium exposure is
   relatively high, there have been no reports of any toxic side-effects.

   This may not be the case with indium compounds: there is some
   unconfirmed evidence that suggests that indium has a low level of
   toxicity. Other sources are more definite about indium compounds'
   toxicity - for example, the WebElements website states that "All indium
   compounds should be regarded as highly toxic. Indium compounds damage
   the heart, kidney, and liver, and may be teratogenic." For example,
   indium trichloride anhydrous (InCl3) is quite toxic, while indium
   phosphide (InP) is both toxic and a suspected carcinogen.

   Retrieved from " http://en.wikipedia.org/wiki/Indium"
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   with only minor checks and changes (see www.wikipedia.org for details
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