   #copyright

Germanium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements

          Note: This article title may be easily confused with Geranium..


                32              gallium ← germanium → arsenic
                Si
                ↑
                Ge
                ↓
                Sn

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                    Name, Symbol, Number germanium, Ge, 32
                                                Chemical series metalloids
                                             Group, Period, Block 14, 4, p
                                                  Appearance grayish white
                                               Atomic mass 72.64 (1) g/mol
                               Electron configuration [Ar] 3d^10 4s^2 4p^2
                                           Electrons per shell 2, 8, 18, 4
                                                       Physical properties
                                                               Phase solid
                                      Density (near r.t.) 5.323 g·cm^−3
                                    Liquid density at m.p. 5.60 g·cm^−3
                                                  Melting point 1211.40  K
                                               (938.25 ° C, 1720.85 ° F)
                                                      Boiling point 3106 K
                                                    (2833 ° C, 5131 ° F)
                                         Heat of fusion 36.94 kJ·mol^−1
                                     Heat of vaporization 334 kJ·mol^−1
                         Heat capacity (25 °C) 23.222 J·mol^−1·K^−1

   CAPTION: Vapor pressure

                                      P/Pa   1    10  100  1 k  10 k 100 k
                                     at T/K 1644 1814 2023 2287 2633 3104

                                                         Atomic properties
                                     Crystal structure Face-centered cubic
                                                        Oxidation states 4
                                                       ( amphoteric oxide)
                                    Electronegativity 2.01 (Pauling scale)
                                                       Ionization energies
                                             ( more) 1st: 762 kJ·mol^−1
                                                  2nd: 1537.5 kJ·mol^−1
                                                  3rd: 3302.1 kJ·mol^−1
                                                      Atomic radius 125 pm
                                              Atomic radius (calc.) 125 pm
                                                    Covalent radius 122 pm
                                                             Miscellaneous
                                                 Magnetic ordering no data
                       Thermal conductivity (300 K) 60.2 W·m^−1·K^−1
                        Thermal expansion (25 °C) 6.0 µm·m^−1·K^−1
                               Speed of sound (thin rod) (20 °C) 5400 m/s
                                                         Mohs hardness 6.0
                                             CAS registry number 7440-56-4
                                                         Selected isotopes

                CAPTION: Main article: Isotopes of germanium

                                 iso    NA   half-life DM DE ( MeV)  DP
                                ^68Ge syn    270.8 d   ε  -         ^68Ga
                                ^70Ge 21.23% Ge is stable with 38 neutrons
                                ^71Ge syn    11.26 d   ε  -         ^71Ga
                                ^72Ge 27.66% Ge is stable with 40 neutrons
                                ^73Ge 7.73%  Ge is stable with 41 neutrons
                                ^74Ge 35.94% Ge is stable with 42 neutrons
                                ^76Ge 7.44%  Ge is stable with 44 neutrons

                                                                References

   Germanium ( IPA: /dʒə(r)ˈmeɪniəm/) is a chemical element in the
   periodic table that has the symbol Ge and atomic number 32. This is a
   lustrous, hard, silver-white metalloid that is chemically similar to
   tin. Germanium forms a large number of organometallic compounds and is
   an important semiconductor material used in transistors.

Notable characteristics

   Germanium is a hard, grayish-white element that has a metallic luster
   and the same crystal structure as diamond. In addition, it is important
   to note that germanium is a semiconductor, with electrical properties
   between those of a metal and an insulator. In its pure state, this
   metalloid is crystalline, brittle and retains its lustre in air at room
   temperature. Zone refining techniques have led to the production of
   crystalline germanium for semiconductors that have an impurity of only
   one part in 10^10.

History

   In 1871 germanium (Latin Germania for Germany) was one of the elements
   that Dmitri Mendeleev predicted to exist as a missing analogue of the
   silicon group (Mendeleev called it " ekasilicon"). The existence of
   this element was proven by Clemens Winkler in 1886. This discovery was
   an important confirmation of Mendeleev's idea of element periodicity.
        Property      Ekasilicon Germanium
   atomic mass        72         72.59
   density (g/cm³)    5.5        5.35
   melting point (°C) high       947
   colour             gray       gray

   The development of the germanium transistor opened the door to
   countless applications of solid state electronics. From 1950 through
   the early 1970s, this area provided an increasing market for germanium,
   but then high purity silicon began replacing germanium in transistors,
   diodes, and rectifiers. Silicon has superior electrical properties, but
   requires much higher purity samples—a purity which could not be
   commercially achieved in the early days. Meanwhile, demand for
   germanium in fibre optics communication networks, infrared night vision
   systems, and polymerization catalysts increased dramatically. These end
   uses represented 85% of worldwide germanium consumption for 2000.

Applications

   Unlike most semiconductors, germanium has a small band gap, allowing it
   to efficiently respond to infrared light. It is therefore used in
   infrared spectroscopes and other optical equipment which require
   extremely sensitive infrared detectors. Its oxide's index of refraction
   and dispersion properties make germanium useful in wide-angle camera
   lenses and in microscope objective lenses.

   Germanium transistors are still used in some stompboxes by musicians
   who wish to reproduce the distinctive tonal character of the
   "fuzz"-tone from the early rock and roll era. Vintage stompboxes known
   to contain germanium transistors have shown marked increases in
   collector value for this reason alone.

   The alloy Silicon germanide (commonly referred to as
   "silicon-germanium", or SiGe) is rapidly becoming an important
   semiconductor material, for use in high speed integrated circuits.
   Circuits utilising the properties of Si-SiGe junctions can be much
   faster than those using silicon alone.
   Germanium bowl
   Enlarge
   Germanium bowl

   Other uses:
     * Alloying agent (see below)
     * Phosphor in fluorescent lamps
     * catalyst
     * High purity germanium single crystal detectors can precisely
       identify radiation sources (e.g. for airport security)
     * Germanium substrate wafers for high-efficiency multi-junction solar
       cells for space applications

   Certain compounds of germanium have low toxicity to mammals, but have
   toxic effects against certain bacteria. This property makes these
   compounds useful as chemotherapeutic agents.

   Germanium is useful for single crystal neutron or synchrotron X-ray
   monochromator for beamlines. The reflectivity has advantages over
   silicon in neutron and High energy X-ray applications.

   While germanium has been claimed as an attractive nutritional supply,
   able to cure even cancer and AIDS, FDA research has concluded that the
   offered supplements "present potential human health hazard".

   In recent years germanium has seen increasing use in precious metal
   alloys. In sterling silver alloys, for instance, it has been found to
   reduce firescale, increase tarnish resistance, and increase the alloy's
   response to precipitation hardening (see Argentium sterling silver).

Occurrence

   This element is found in argyrodite ( sulfide of germanium and silver);
   coal; germanite; zinc ores; and other minerals. See also
   Category:Germanium minerals

   Germanium is obtained commercially from zinc ore processing smelter
   dust and from the combustion by-products of certain coals. A large
   reserve of this element is therefore in coal sources.

   This metalloid can be extracted from other metals by fractional
   distillation of its volatile tetrachloride. This technique permits the
   production of ultra-high purity germanium.

Value

   In 1998 the cost of germanium was about US$3 per gram. The yearend
   price for zone-refined germanium has (generally) decreased since then:

                2000.....$1,150 per kilogram (or $1.15 per gram)
                2001.....$890 per kilogram (or $0.89 per gram)
                2002.....$620 per kilogram (or $0.62 per gram)
                2003.....$380 per kilogram (or $0.38 per gram)
                2004.....$600 per kilogram (or $0.60 per gram)
                2005.....$610 per kilogram (or $0.61 per gram)
                2006.....$720 per kilogram (or $0.72 per gram)

Compounds

   Some inorganic germanium compounds include Germane or Germanium
   tetrahydride (GeH[4]), Germanium tetrachloride (GeCl[4]), and Germanium
   dioxide (germania) (GeO[2]). Some organic compounds of germanium
   include tetramethylgermane or tetramethyl germanium, (Ge(CH[3])[4]),
   and tetraethylgermane or tetraethyl germanium, (Ge(C[2]H[5])[4]).
   Recently a new organogermanium compound isobutylgermane
   ((CH[3])[2]CHCH[2]GeH[3]), was reported as the less hazardous liquid
   substitute for toxic germane gas in semiconductor applications.

   See also Category:Germanium compounds
   Retrieved from " http://en.wikipedia.org/wiki/Germanium"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
