GERMANIUM

Name: Germanium (from the Latin name for Germany, "Germania")

Symbol: Ge

Group: 14

Period: 4

Block: p

Category: Metalloids

Atomic Number: 32

Atomic Mass: 72.630 u

Electrons per Shell: 2, 8, 18, 4

Electronegativity: 2.01

Density: 5.323 g/cc

Melting Point: 938.25ºC

Boiling Point: 2833ºC

Thermal Conductivity: 60 W (m K)

Electrical Conductivity: 2000 S/m

Magnetic Order: Diamagnetic

Ordinary State: Solid

Oxidation States: -4, -3, -2, 0, -1, 1, 2, 3, 4

Mohs Hardness: 6

Vickers Hardness: 8012 MPa

Brinell Hardness: No data

Most stable isotopes: Ge-70 (20.52%), Ge-72 (27.45%), Ge-73 (7.76%), Ge-74 (36.52%), Ge-76 (7.75%)

Discoverer: Clemens Winkler, German (1886)

Germanium (Ge), chemical element with atomic number 32, is a metalloid of group 14 with a density of 5.32 g/cm³ and an abundance of approximately 1.5 ppm in the Earth's crust, making it significantly scarcer than its analogue, silicon (Si, ~282,000 ppm). Sharing chemical and physical properties with silicon due to its position in the carbon (C) group, germanium has a silvery-gray appearance with a metallic luster, but its rarity and lack of mechanical strength limit its structural applications. Its importance lies in electronics and optics, where its semiconductor properties are fundamental.

Germanium was first isolated in 1886 by the German chemist Clemens Winkler in Freiberg, during the analysis of the mineral argyrodite (Ag₈GeS₆). Winkler reduced the mineral with hydrogen and obtained pure germanium, naming it in honor of Germania, the Latin term for the region encompassing present-day Germany, Austria, and nearby areas. This discovery, published in the Journal für Praktische Chemie, confirmed Dmitri Mendeleev's prediction, who in 1871 had proposed the existence of an element, which he called "ekasilicon," to fill a gap in his periodic table. The identification of germanium validated the accuracy of Mendeleev's table and marked a milestone in 19th-century chemistry.

Although known indirectly since antiquity through minerals such as germanite, germanium had no significant applications until the 20th century. During World War II, its potential as a semiconductor began to be explored, and with the development of the transistor in 1947, germanium became a key material in early electronics, before being surpassed by silicon due to its greater abundance and lower cost. In 2025, global germanium production (130 annual tons) focuses on high-tech applications, such as fiber optics, infrared detectors, and solar cells, reflecting its relevance in modern industry despite its scarcity (50–100 USD/kg).

Germanium (Ge), with atomic number 32, is a metalloid of group 14, with a density of 5.32 g/cm³ and an abundance of approximately 1.5 ppm in the Earth's crust, making it significantly scarcer than silicon (Si, 282,000 ppm). Its appearance is a metallic beige color, reminiscent of aged bronze, with a mirror-like reflective luster, especially in its pure crystalline form, which can achieve purities greater than 99.999% through processes like zone refining or the Czochralski method, although these are costly (50–100 USD/kg in 2025). As a metalloid, it shares chemical and physical properties with silicon, serving as the standard of comparison for other group 14 metalloids, and excels in electronic applications due to its semiconductor properties.

Elemental germanium is notably resistant to corrosion, surpassing silicon in high-temperature conditions. It forms a protective layer of germanium oxide (GeO₂) that stabilizes it against common acids, such as sulfuric acid (H₂SO₄) or hydrochloric acid (HCl), although it is vulnerable to hydrofluoric acid (HF) and strong hot alkalis like sodium hydroxide (NaOH). Its chemical resistance makes it suitable for corrosive environments, although its brittleness limits its structural use. With a hardness of approximately 6 on the Mohs scale, germanium is hard but brittle, and can be easily pulverized under dry impacts. Its compressive strength is high (~8 GPa), comparable to ceramic materials, but its low impact resistance makes it unsuitable for applications subject to mechanical impacts.

In terms of conductivity, germanium is a poor thermal conductor (60 W/(m·K)) and electrical conductor (2.17 S/m undoped) compared to metals like copper (Cu, 400 W/(m·K), ~5.9 × 10⁷ S/m). However, its semiconductor properties are exceptional, with a band gap of 0.67 eV that allows for high electron mobility, especially when doped with elements like arsenic (As) or gallium (Ga). This makes it ideal for transistors, diodes, and infrared detectors, although it has been partially replaced by silicon in electronics due to the latter's lower cost and greater abundance. Its melting point, 938.3°C, is lower than that of silicon (1414°C), facilitating its processing, but its brittleness and cost limit its use in its pure state. Global germanium production (130 annual tons in 2025) is concentrated in high-tech applications, where its corrosion resistance and electronic properties make it indispensable.

Germanium, with atomic number 32, is a metalloid of group 14, with a density of 5.32 g/cm³ and an abundance of approximately 1.5 ppm in the Earth's crust, making it much scarcer than silicon. Its global production, around 130 annual tons in 2025, reflects its high cost (~50–100 USD/kg) and its use in high-tech applications. Despite its brittleness and lack of structural applications, germanium stands out for its semiconductor and optical properties, being essential in electronics, optics, and, to a lesser extent, jewelry, where its corrosion resistance and ability to form passivating layers improve the properties of alloys.

The most significant use of germanium is in the manufacture of fiber optics, where it is employed in both elemental form and as germanium oxide (GeO₂) to form the core of the fibers. This material enhances light refraction, increasing transmission efficiency compared to titanium oxide (TiO₂), which required thermal treatments that weakened the fiber. Germanium allows for more robust and durable fibers, essential for telecommunications and high-speed networks, representing a significant portion of its global consumption. In the electronics industry, germanium is a key semiconductor material, with a band gap of 0.67 eV that facilitates high electron mobility. Doped with gallium (Ga) or arsenic (As), it is used in transistors, diodes, and solar cells, although it has been partially replaced by silicon due to its lower cost and greater abundance. Its electrical conductivity (2.17 S/m undoped) and thermal conductivity (60 W/(m·K)) make it ideal for high-precision applications.

In optics, germanium oxide (GeO₂) is incorporated into specialized crystals for infrared camera lenses and infrared radiation detectors, leveraging its high transparency in the infrared range (2–17 µm). These properties make it indispensable in night vision systems, spectroscopy, and military applications. In jewelry, germanium plays a unique role in the Argentium silver alloy, developed in the 1990s by Peter Johns in the United Kingdom. This alloy, with a minimum silver content of 92.5% (classified as sterling silver), incorporates small amounts of germanium (a patented proportion) instead of part of the copper (Cu) present in sterling silver (Ag 92.5%, Cu 7.5%) or Britannia silver (Ag 95%). Germanium forms a passivating layer of germanium oxide (GeO₂) that protects the surface against environmental sulfur, preventing the typical tarnishing (sulfurization) of silver alloys. This layer, analogous to alumina (Al₂O₃) in aluminum bronzes, improves wear resistance and galling (friction deformation), giving Argentium a lasting, attractive white luster. Although more expensive than sterling silver, its ease of workability and superior aesthetics make it popular, although its manufacture is restricted to licensed companies due to the trademark.

Germanium's corrosion resistance, especially when hot, distinguishes it in these applications. It resists common acids, except hydrofluoric acid (HF), and forms protective layers that stabilize alloys. Its brittleness (~6 Mohs, 8 GPa compressive strength) limits its use in its pure state, but its incorporation into alloys and compounds, along with its low toxicity compared to metals like lead (Pb), ensures its relevance in modern technologies, from telecommunications to high-quality jewelry.