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Gallium

physical science Maturity 7-9 Next article →

Gallium is a chemical element with the symbol Ga and the atomic number 31. It is a soft, silvery metal when it is a solid at standard temperature and pressure.

6N Gallium sealed in vacuum ampoule
6N Gallium sealed in vacuum ampoule

In its liquid state, the metal appears silvery white. Gallium is highly significant in modern science because of its unique physical and chemical properties. It serves as a vital component in the electronics industry and acts as a precise reference point for measuring temperature. Because it can exist as a liquid near room temperature, it offers many uses that other metals cannot provide.

The physical behavior of gallium is driven by its unique atomic structure. In its stable solid phase, gallium has an orthorhombic structure with eight atoms in its conventional unit cell. Within this structure, atoms form Ga2 dimers, which are pairs of atoms held together by covalent bonds.

Gallium kristallisiert
Gallium kristallisiert

These dimers act as the fundamental building blocks of the crystal. This specific bonding explains why gallium has such a low melting point compared to its neighbors, aluminum and indium. When gallium melts, these dimers do not persist. Instead, the liquid exhibits a complex structure where each atom is surrounded by ten others.

One of the most remarkable features of gallium is its melting point, which is 29.7646 °C (85.5763 °F). This temperature is just above standard room temperature and is similar to average summer daytime temperatures in Earth's mid-latitudes.

Liquid gallium pouring
Liquid gallium pouring

Because of this, elemental gallium will melt in a person's hand at a normal body temperature of 37 °C. Gallium is one of only four non-radioactive metals that are liquid or near-liquid at room temperature. These others are caesium, rubidium, and mercury. Unlike rubidium and caesium, gallium is not highly reactive. Unlike mercury, it is not highly toxic. This makes it a safer choice for many applications.

Gallium's phase changes require careful handling due to its expansion properties. When gallium changes from a liquid to a solid, its volume expands by 3.10%. This is similar to how water expands when it freezes. If gallium is stored in a container that is too tight, this expansion can cause the container to rupture. Additionally, liquid gallium has a strong tendency to supercool. This means it can remain in a liquid state even when cooled below its freezing point. Scientists can initiate freezing by using a process called seeding with a crystal.

The history of gallium began in 1875. The French chemist Paul-Émile Lecoq de Boisbaudran discovered the element in Paris, France.

Bauxite Jamaica 1984
Bauxite Jamaica 1984

Gallium does not occur as a free element in nature. Instead, it is found in trace amounts within gallium(III) compounds. These are located in zinc ores, such as sphalerite, and in bauxite. The metal is obtained through a process called smelting. This allows humans to extract the pure element from these mineral sources.

In the field of electronics, gallium is indispensable. It is used to create semiconductors, which are materials that control the flow of electricity. Gallium arsenide is a primary compound used in high-speed switching circuits, microwave circuits, and infrared circuits.

Blue LED and Reflection
Blue LED and Reflection

Other compounds, such as gallium nitride and indium gallium nitride, are used to produce blue and violet light-emitting diodes (LEDs) and diode lasers. Gallium is also used to produce artificial gadolinium gallium garnet for jewelry. Even in medicine, gallium-67 and gallium-68 are used for imaging in nuclear medicine scans.

Gallium is also used to create specialized alloys with very low melting points. One such alloy is called galinstan. Galinstan is composed of 62–95% gallium, 5–22% indium, and 0–16% tin by weight.

Galinstan on glass
Galinstan on glass

This alloy is used in thermometers as a non-toxic and environmentally friendly alternative to mercury. Because galinstan can withstand higher temperatures than mercury, it is a very useful tool. Furthermore, gallium can be used to create brilliant mirrors when it is painted onto glass. This ability to wet surfaces makes it mechanically difficult to handle, but highly useful for optical applications.

Gallium alloy 3D prints (26519727708)
Gallium alloy 3D prints (26519727708)
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🖼️ Images & Media (8)
File:Gallium kristallisiert.JPG
Gallium kristallisiert.JPG
File:Liquid gallium pouring.png
Liquid gallium pouring.png
Gallium drops.ogv
File:6N Gallium sealed in vacuum ampoule.jpg
6N Gallium sealed in vacuum ampoule.jpg
File:Bauxite Jamaica 1984.jpg
Bauxite Jamaica 1984.jpg
File:Blue LED and Reflection.jpg
Blue LED and Reflection.jpg
File:Galinstan on glass.jpg
Galinstan on glass.jpg
File:Gallium alloy 3D prints (26519727708).jpg
Gallium alloy 3D prints (26519727708).jpg
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