- Germanium (Ge) is a lustrous, grayish-white metalloid with atomic number 32, positioned in Group 14 of the periodic table, between silicon and tin.
- It exhibits properties intermediate between metals and nonmetals, making it important in semiconductors and optical technologies. Germanium has four valence electrons in the 4s and 4p subshells, and it commonly exhibits oxidation states of +4 and, less frequently, +2. Its atomic structure consists of thirty-two protons, typically forty-one neutrons, and thirty-two electrons arranged in four shells.
- Naturally occurring germanium consists of five stable isotopes: germanium-70 (⁷⁰Ge, 20.84%), germanium-72 (⁷²Ge, 27.54%), germanium-73 (⁷³Ge, 7.73%), germanium-74 (⁷⁴Ge, 36.28%), and germanium-76 (⁷⁶Ge, 7.61%), the last of which is weakly radioactive with an extremely long half-life.
- Germanium is relatively rare in Earth’s crust, occurring at about 1.6 parts per million. It is not found in concentrated ores but is dispersed in minerals such as argyrodite (Ag₈GeS₆), germanite (Cu₁₃Fe₂Ge₂S₁₆), and in trace amounts within sphalerite (ZnS), from which most germanium is recovered as a by-product of zinc mining. Coal ash can also contain recoverable germanium. Major producing countries include China, Russia, Canada, and the United States.
- The element was predicted by Dmitri Mendeleev in 1869 as “eka-silicon,” a yet-undiscovered element beneath silicon in the periodic table. In 1886, German chemist Clemens Winkler discovered germanium in the mineral argyrodite and found its properties matched Mendeleev’s predictions closely, confirming the predictive power of the periodic table. Winkler named the element after his homeland, Germany (Germania in Latin).
- Germanium’s most important applications are in electronics and optics. High-purity germanium is a semiconductor with properties similar to silicon but with higher carrier mobility, making it useful in high-speed integrated circuits, fiber-optic systems, and infrared optics. Although silicon has largely replaced germanium in transistors since the 1960s, germanium remains important in niche high-performance semiconductor devices, such as those used in space and military applications. Germanium dioxide (GeO₂) is a key material for producing the glass cores of optical fibers, enhancing their refractive index and transmission properties.
- In infrared technology, germanium is prized for its transparency to infrared radiation and its high refractive index, making it a material of choice for lenses, windows, and thermal imaging systems. It is also used in polymerization catalysts, phosphors, and as an alloying agent in certain metals to improve corrosion resistance and mechanical properties.
- Chemically, germanium is relatively inert at room temperature, resisting oxidation and attack by most acids except nitric acid and strong oxidizing agents. At elevated temperatures, it forms germanium dioxide, a white powder that is amphoteric and soluble in both acids and alkalis. Germanium forms a wide range of covalent compounds, including organogermanium derivatives, which are of research interest in materials science and medicine.
- Biologically, germanium has no known essential role in life processes, though some organic germanium compounds have been explored for potential therapeutic uses. However, excessive ingestion of inorganic germanium compounds can lead to kidney damage and other toxic effects.
- From an environmental standpoint, germanium is not considered highly toxic in its elemental form, but some of its compounds, especially in dust or fume form, require careful handling. Due to its relatively low natural abundance and increasing demand in advanced technologies, recycling of germanium from optical devices, electronics, and catalyst residues is an important part of its supply chain.
