Germanium (Ge)

Stable isotopes of germanium available from ISOFLEX

Isotope Z(p) N(n) Atomic Mass Natural Abundance Enrichment Level Chemical Form
Ge-70  32  38 69.924249 20.38% 95.30-97.60% Metal
Ge-70 32 38 69.924249 20.38% 95.30-97.60% Oxide
Ge-72  32  40  71.922076 27.31%  96.40-98.20% Metal
Ge-72 32 40 71.922076 27.31% 96.40-98.20% Oxide
Ge-73 32 41 72.923460 7.76% 95.60-99.40% Metal
Ge-73 32 41 72.923460 7.76% >95.50% Oxide
Ge-74 32 42 73.921178 36.72% 97.50-99.80% Metal
Ge-74 32 42 73.921178 36.72% ≥95.20% Oxide
Ge-76 32 44 75.921403 7.83% >99.90% Metal
Ge-76 32 44 75.921403 7.83% 88.00-99.90% Oxide

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Germanium was discovered in 1886 by Clemens Winkler. Its name originates with the Latin name Germania, meaning “Germany.”

Germanium is a grayish-white cubic crystal. Elemental germanium can be prepared in extreme purification with a high degree of crystalline perfection, so as to yield highly-characterized surfaces. Its conductivity depends largely on added impurities. It is attacked by nitric acid and aqua regia, but it is stable in water, acids and alkalis in the absence of dissolved oxygen. It is insoluble in water, dilute acids and dilute alkalis. The chemical properties of germanium fall between those of silicon and tin. It forms both the divalent and tetravalent compounds, the oxidation state +4 being more stable than the oxidation state +2. The metal is stable in air and water at ambient temperatures. However, it reacts with oxygen at elevated temperatures, forming divalent and tetravalent oxides. 

The most important uses of germanium are in electronic industries. It is a semiconductor material exhibiting an exponential increase of conductivity with increasing temperature. Other applications include infrared detectors, microscopes, various optical instruments, as a phosphor in fluorescent lamps, as an alloying agent, and as a catalyst. The activity of some germanium compounds against certain bacteria makes them of interest as chemotherapeutic agents.

Properties of Germanium

Name Germanium 
Symbol Ge 
Atomic number 32 
Atomic weight 72.61 
Standard state Solid at 298 °K 
CAS Registry ID 7440-56-4 
Group in periodic table 14 
Group name None 
Period in periodic table
Block in periodic table p-block 
Color Grayish-white 
Classification Semi-metallic 
Melting point 938.2 °C
Boiling point 2830 °C
Thermal conductivity 60.2 W/(m·K) at 302.93 °K 
Electrical resistivity 47 µΩ·cm at 20 ºC 
Electronegativity 1.8 
Specific heat 0.322 J/g mol at 20 ºC 
Heat of vaporization 334 kJ·mol-1 at 2830 ºC 
Heat of fusion 31.8 kJ·mol-1 
Density of liquid 5.60 g/cm
Density of solid 5.32 g/cm
Electron configuration  [Ar]3d104s24p2 
Oxidation states +2, +4 
Electronegativity  1.9
Covalent radius  (Tetrahedral, sp3) 1.22 Å
Ionic radius Ge2+: 0.93 Å, Ge4+: 0.53 Å 

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