- Gallium (Ga) is a soft, silvery metallic element with atomic number 31, positioned in Group 13 of the periodic table.
- It is notable for its low melting point of about 29.76 °C, meaning it can melt in the hand, while having a high boiling point of about 2,204 °C. Gallium has three valence electrons—two in the 4s subshell and one in the 4p subshell—and most commonly exhibits oxidation states of +3 and, less frequently, +1. Its atomic structure consists of thirty-one protons, typically thirty-nine neutrons, and thirty-one electrons arranged in four shells.
- Naturally occurring gallium consists of two stable isotopes: gallium-69 (⁶⁹Ga), which makes up about 60.11%, and gallium-71 (⁷¹Ga), which comprises about 39.89%.
- Gallium is not found as a free metal in nature; instead, it occurs in trace amounts within minerals such as bauxite (aluminum ore) and sphalerite (zinc ore). It is obtained mainly as a by-product of aluminum production from bauxite and zinc extraction from sphalerite. The largest producers are China, Russia, Germany, and Ukraine, though gallium is recovered in small amounts worldwide due to its occurrence in common ores.
- The element was discovered in 1875 by French chemist Paul-Émile Lecoq de Boisbaudran through spectroscopic analysis, where he observed its characteristic violet spectral lines. Soon after, he isolated gallium by electrolysis of gallium hydroxide in potassium hydroxide solution. The discovery of gallium confirmed Dmitri Mendeleev’s prediction of an element he called “eka-aluminum,” filling a gap in the periodic table. The name “gallium” is derived from the Latin Gallia for France, and possibly also from Lecoq’s own surname (“le coq” meaning “rooster” in French, and gallus in Latin).
- Gallium’s unusual combination of a low melting point and a high boiling point makes it valuable in specialized applications. Gallium arsenide (GaAs) is a key semiconductor material used in high-speed electronics, light-emitting diodes (LEDs), laser diodes, and photovoltaic cells, particularly in space-based solar panels due to its high efficiency and resistance to radiation damage. Gallium nitride (GaN) is another important compound used in power electronics, blue and white LEDs, and microwave-frequency transistors.
- In its pure form, gallium wets glass and most metals, making it useful in certain mirrors and seals. Its ability to alloy with many metals, including lowering the melting points of alloys, is exploited in producing low-melting-point materials for temperature-sensitive applications. Gallium-based alloys such as galinstan (gallium–indium–tin) are non-toxic liquid metal alternatives to mercury in thermometers and other devices.
- Chemically, gallium is stable in air at room temperature but forms a thin oxide layer on its surface. It reacts slowly with mineral acids and alkalis, forming gallium(III) salts or gallates. Gallium does not crystallize in a simple cubic or hexagonal close-packed structure; instead, it has a unique orthorhombic structure with strong directional bonds, which contributes to its unusual melting behavior.
- Biologically, gallium has no known natural role in living organisms, but gallium salts can interfere with biological processes involving iron due to their chemical similarity, making them useful in certain medical treatments. Gallium nitrate is used in medicine to treat hypercalcemia associated with cancer, and radioactive gallium isotopes (e.g., gallium-67) are used in medical imaging.
- Environmentally, gallium is considered to have low toxicity, though some compounds, such as gallium arsenide, are toxic due to their arsenic content. With the growth of electronics manufacturing, gallium recycling from semiconductor waste and end-of-life solar panels is becoming increasingly important to secure supply and reduce environmental impact.
