Difference between revisions of "Germanium"
| Line 304: | Line 304: | ||
:GeO<sub>2</sub> + C → Ge + CO<sub>2</sub> | :GeO<sub>2</sub> + C → Ge + CO<sub>2</sub> | ||
| − | Unlike in the case of silicon, this reduction will yield only a small quantity of carbide. | + | Unlike in the case of silicon, this reduction will yield only a small quantity of germanium carbide. |
==Projects== | ==Projects== | ||
Revision as of 22:45, 19 November 2019
| General properties | |||||
|---|---|---|---|---|---|
| Name, symbol | Germanium, Ge | ||||
| Allotropes | α-Ge, β-Ge | ||||
| Appearance | Lustrous gray | ||||
| Germanium in the periodic table | |||||
| |||||
| Atomic number | 32 | ||||
| Standard atomic weight (Ar) | 72.630(8) | ||||
| Group, block | (carbon group); p-block | ||||
| Period | period 4 | ||||
| Electron configuration | [Ar] 3d10 4s2 4p2 | ||||
per shell | 2, 8, 18, 4 | ||||
| Physical properties | |||||
| Lustrous gray | |||||
| Phase | Solid | ||||
| Melting point | 1211.40 K (938.25 °C, 1720.85 °F) | ||||
| Boiling point | 3106 K (2833 °C, 5131 °F) | ||||
| Density near r.t. | 5.323 g/cm3 | ||||
| when liquid, at | 5.60 g/cm3 | ||||
| Heat of fusion | 36.94 kJ/mol | ||||
| Heat of | 334 kJ/mol | ||||
| Molar heat capacity | 23.222 J/(mol·K) | ||||
| pressure | |||||
| Atomic properties | |||||
| Oxidation states | 4, 3, 2, 1, 0, −1, −2, −3, −4 (an amphoteric oxide) | ||||
| Electronegativity | Pauling scale: 2.01 | ||||
| energies |
1st: 762 kJ/mol 2nd: 1537.5 kJ/mol 3rd: 3302.1 kJ/mol | ||||
| Atomic radius | empirical: 122 pm | ||||
| Covalent radius | 122 pm | ||||
| Van der Waals radius | 211 pm | ||||
| Miscellanea | |||||
| Crystal structure | Face-centered diamond-cubic | ||||
| Speed of sound thin rod | 5400 m/s (at 20 °C) | ||||
| Thermal expansion | 6.0 µm/(m·K) | ||||
| Thermal conductivity | 60.2 W/(m·K) | ||||
| Electrical resistivity | 1 Ω·m (at 20 °C) | ||||
| Young's modulus | 103 GPa | ||||
| Shear modulus | 41 GPa | ||||
| Bulk modulus | 75 GPa | ||||
| Poisson ratio | 0.26 | ||||
| Mohs hardness | 6.0 | ||||
| CAS Registry Number | 7440-56-4 | ||||
| History | |||||
| Naming | After Germany, homeland of the discoverer | ||||
| Prediction | Dmitri Mendeleev (1871) | ||||
| Discovery | Clemens Winkler (1886) | ||||
Germanium is a chemical element with symbol Ge and atomic number 32. It is a metalloid.
Contents
Properties
Chemical
Elemental germanium is stable in air, and slowly oxidizes to GeO2 at 250 °C. Germanium is insoluble in dilute acids and alkali, but reacts slowly with concentrated sulfuric acid and violently with molten alkali to produce germanates ([GeO3]2−).
Germanium halides hydrolyze in water or moist air.
Physical
Germanium is a brittle, silvery-white, semi-metallic element. It posses two allotrope forms:
- α-germanium: the form at standard conditions. It has a metallic luster and a diamond cubic crystal structure.
- β-germanium: forms at pressures above 120 kbar. It posses the same structure as β-tin.
Extremely pure germanium will spontaneously extrude very long screw dislocations. This is the primary reason why old transistors fail.
Along with antimony, bismuth, gallium, silicon and water, it is one of the few substances that expands as it solidifies. Germanium is a semiconductor.
Availability
Germanium can be found in very old transistors and diodes, albeit the amount is small.
Pure germanium can be purchased from Metallium, at $11/g. It is very easy to find extremely pure germanium, as it is used in certain semiconductors.
Preparation
Elemental germanium can be prepared by reducing germanium dioxide (germania) with hydrogen.
- GeO2 + H2 → Ge + H2O
This reaction requires high temperatures.
Germanium is less reactive than silicon, so carbon can also be used as a reducing agent.
- GeO2 + C → Ge + CO2
Unlike in the case of silicon, this reduction will yield only a small quantity of germanium carbide.
Projects
- Make germanium dioxide
- Make germane (GeH4)
Handling
Safety
Pure germanium has low toxicity, however its compounds have different biological effects. Inorganic germanium compounds tend to accumulate inside the body and will cause health related problems. Organic germanium compounds have been shown to be less toxic and some even have beneficial properties.
Storage
Germanium reacts very slowly in air to produce a thin protective layer of germania. No special storage is required.
Disposal
Germanium is present only in traces in nature. Germania is inert so it does not pose environmental hazard, and may be dumped in the trash. Inorganic germanium compounds should be converted to germania before discarding or recycling.
