Gallium
Gallium is a chemical element with symbol Ga and atomic number 31. Elemental gallium does not occur in free form in nature, but as the gallium(III) compounds that are in trace amounts in zinc ores and in bauxite. Gallium is a soft, silvery metal, and elemental gallium is a brittle solid at low temperatures, and melts at 29.76 °C (85.57 °F) (slightly above room temperature).
Identity
- Atomic mass
- 69.723 u
- Category
- Post-transition metals
- Group
- 13
- Period
- 4
- Block
- p
- Oxidation States
- +1, +3
- Phase (25 °C)
- Solid
- Appearance
- silver-white
Electronic Structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p1
- Short configuration
- [Ar] 3d10 4s2 4p1
- Electrons per shell
- 2, 8, 18, 3
- Electronegativity (Pauling)
- 1.81
- Electron affinity
- 41 kJ/mol
- 1st ionization energy
- 579 kJ/mol
- Ionization energies
- 579 · 1979 · 2963 · 6180 kJ/mol
Physical properties
- Melting point
- 29.8 °C (303 K)
- Boiling point
- 2399.8 °C (2673 K)
- Density
- 5.91 g/cm³
- Molar heat capacity
- 25.9 J/(mol·K)
Chemical behavior of gallium
Gallium is a metalloid of group 13 (boron family) that presents the oxidation states +1 and +3, +3 being the most stable and most frequent in its chemistry. Its electronegativity of 1.81 (Pauling scale) configures it as an element with properties intermediate between metals and non-metals, with a tendency to covalency. Its predominant bond is covalent, with a tendency to form four bonds directed tetrahedrally in its compounds. Exceptions: metallic gallium presents moderate electrical conductivity and metallic properties, with a melting point of only 29.76 °C (almost room temperature), which gives it an electro-thermal conductivity sensitive to heat.
Reactivity
2 Ga + 3 Cl2 -> 2 GaCl3
Gallium reacts with chlorine to give gallium(III) chloride, a white volatile solid that is the precursor of numerous gallium and gallate derivatives.
Ga2O3 + 2 NaOH + 3 H2O -> 2 NaGa(OH)4
Gallium oxide reacts with strong base forming sodium gallate, showing gallium's amphoteric character in basic medium.
Notable compounds
| Compound | Formula | Use or importance |
|---|---|---|
| Gallium nitride | GaN | Semiconductor capable of emitting blue and violet light; key for high-efficiency blue LEDs |
| Gallium arsenide | GaAs | High-frequency semiconductor; used in communications, optoelectronic devices and power |
| Gallium phosphide | GaP | Luminescent semiconductor; used in light-emitting diodes and photovoltaic cells |
| Gallium(III) oxide | Ga2O3 | Terminator material for high-voltage power devices |
Electron shell distribution
View in the atom builderIsotopes
Natural gallium is composed of two stable isotopes: gallium-69 (⁶⁹Ga, 60.108%) and gallium-71 (⁷¹Ga, 39.892%). Both are non-radioactive and stable. The isotope 69Ga is the most abundant.
Occurrence and production
Gallium is a trace element in the Earth's crust, with a concentration of about 0.0018-0.002 ppm. It occurs mainly combined in germanite and in zinc minerals, where it is found in minor traces. It is obtained mainly as a byproduct of aluminium (bauxite) and copper refining. The main reserves are in China, Japan, South Korea, Russia and Canada.
History and origin of the name
Dmitri Mendeleev predicted its existence in 1871, baptising the element 'eka-aluminium'. Its existence was experimentally confirmed in 1875 by the French chemist Paul Émile Lecoq de Boisbaudran, who isolated it from a zinc mineral in the French Pyrenees, and discovered that its properties matched those predicted by Mendeleev. The name 'gallium' derives from the Latin 'Gallia' (France), where it was discovered.
Applications and relevance of gallium
Uses of the element
Metallic gallium is used in specialised applications, especially in low-melting alloys, in cryotronics thermometers and in superconductors. It is also added to certain welding formulations and to high-performance coolants in space and high-power applications.
Uses of its compounds
Gallium compounds are fundamental in modern electronic technology: gallium nitride (GaN) enables the manufacture of blue, violet LEDs and high-efficiency power devices; gallium arsenide (GaAs) is essential in radiofrequency communications, satellites and optoelectronic components; gallium phosphide (GaP) is used in light-emitting diodes; and gallium(III) oxide (Ga₂O₃) appears as a high-power material for energy devices.
Health, safety and environment
Biological role
Gallium is not essential for living things. Gallium salts can be irritating and toxic in high doses. Gallium is absorbed through skin, lungs and gastrointestinal system. Metallic gallium is stable and does not easily dissolve in natural biological environment. Prolonged exposure to gallium dust can cause respiratory irritation.
Safety
Metallic gallium is relatively stable, but gallium salts can be toxic. Exposure to gallium dust can cause skin, eye and respiratory irritation. Gallium can damage some metals by penetrating their structure, especially aluminium. It should be handled with adequate ventilation, hand and eye protection. Waste must be recycled at suitable centres.
Environment
Gallium does not degrade in the environment and its accumulation can affect soils and surface waters. Industrial discharges of gallium compounds can be dangerous for aquatic life, especially if they accumulate in sediments. Gallium in nature is mainly in zinc minerals, and extraction and refining of this rock can release gallium compounds into nature. Proper management of mining waste and electronic panel manufacturing is essential to prevent environmental contamination by gallium.
Frequently asked questions about Gallium
Why does gallium melt in the hand?
Gallium has a melting point close to room temperature, so it can pass from solid to liquid when receiving heat from a hand. This property makes it a striking example of how metals can behave very differently from one another. Unlike common metals, it does not need to reach high temperatures to melt. However, the process depends on the initial temperature of the sample and ambient conditions.
What is the difference between gallium and gallium arsenide?
Gallium is a chemical element, while gallium arsenide (GaAs) is a compound formed by gallium and arsenic. This semiconductor has electronic and optical properties especially useful in high-frequency devices and in technologies that emit or detect light. Gallium also forms other semiconductor compounds, such as gallium nitride. Each material has its own characteristics, so the choice depends on the application: not all gallium-based semiconductors work the same way.
How is gallium used in modern chargers and electronic devices?
Gallium is used in the manufacture of high-efficiency semiconductors such as gallium arsenide (GaAs) and gallium nitride (GaN), which are essential in wireless chargers, high-voltage batteries and communication devices. GaAs is used in radiofrequency components and optoelectronic devices, while GaN allows creating more compact and efficient power supplies for portable devices and appliances.
What role does gallium play in satellite communications?
Semiconductors based on gallium, such as gallium arsenide and gallium nitride, are used in certain satellite communication systems. The first is useful in radiofrequency components and optoelectronic devices, while the second can handle high powers and work with efficiency in specialised amplifiers. These properties help process and transmit signals under demanding conditions. The choice of compound depends on frequency, required power and system thermal limitations.
Why is gallium nitride important for LED lighting?
Gallium nitride (GaN) is a semiconductor capable of emitting light when electrons and holes recombine under certain conditions. Its electronic properties allow the manufacture of blue and violet LEDs, fundamental to many current lighting technologies. By combining blue LEDs with materials that convert part of that light into other colours, efficient white light sources can be obtained. GaN is also used in power electronic devices and components capable of working with high electric fields.
Why can gallium remain liquid at room temperature?
Gallium presents a solid crystalline structure whose stability changes notably near room temperature. When it absorbs sufficient thermal energy, the crystalline structure stops maintaining and the metal melts. A particularity is that it can remain liquid below its melting point if the appropriate conditions to start solidification are not given, a phenomenon known as supercooling. That is why a liquid gallium sample can retain that state for some time even after cooling.
Why can gallium damage some metals?
Liquid gallium can penetrate certain metals, especially aluminium, and alter their mechanical integrity. Under certain conditions, it favours embrittlement phenomena that reduce the material's ability to support stresses without fractures. Therefore, contact between the two materials requires caution in technical applications. This behaviour does not mean that gallium instantly destroys any metal: the effect depends on composition, surface condition, temperature and contact conditions.
Main sources consulted: PubChem, Royal Society of Chemistry, NIST, IUPAC. Last revision: November 2026.