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Gallium,  31Ga
General properties
Name, symbol Gallium, Ga
Appearance Silvery white
Gallium in the periodic table


Atomic number 31
Standard atomic weight (Ar) 69.723(1)
Group, block (boron group); p-block
Period period 4
Electron configuration [Ar] 3d10 4s2 4p1
per shell
2, 8, 18, 3
Physical properties
Phase Solid
Melting point 302.9146 K ​(29.7646 °C, ​85.5763 °F)
Boiling point 2673 K ​(2400 °C, ​​4352 °F)
Density near r.t. 5.91 g/cm3
when liquid, at  6.095 g/cm3
Heat of fusion 5.59 kJ/mol
Heat of 256 kJ/mol
Molar heat capacity 25.86 J/(mol·K)
Atomic properties
Oxidation states 3, 2, 1, −1, −2, −4, −5​(an amphoteric oxide)
Electronegativity Pauling scale: 1.81
energies 1st: 578.8 kJ/mol
2nd: 1979.3 kJ/mol
3rd: 2963 kJ/mol
Atomic radius empirical: 135 pm
Covalent radius 122±3 pm
Van der Waals radius 187 pm
Crystal structure ​Orthorhombic
Speed of sound thin rod 2740 m/s (at 20 °C)
Thermal expansion 18 µm/(m·K) (at 25 °C)
Thermal conductivity 40.6 W/(m·K)
Electrical resistivity 2.7·10-7 Ω·m (at 20 °C)
Magnetic ordering Diamagnetic
Young's modulus 9.8 GPa
Poisson ratio 0.47
Mohs hardness 1.5
Brinell hardness 56.8–68.7 MPa
CAS Registry Number 7440-55-3
Naming After Gallia (Latin for: France), homeland of the discoverer
Prediction Dmitri Mendeleev (1871)
Discovery and first isolation Lecoq de Boisbaudran (1875)
· references

Gallium is a chemical element with symbol Ga and atomic number 31.



Gallium is attacked by acids and free halogens, but does not react with air or water at room temperature, only at high temperatures, producing gallium(III) oxide Ga2O3. If Ga2O3 is reduced with elemental gallium in vacuum at 500-700 °C, it will yield the dark brown gallium(I) oxide, Ga2O.

Ga2O3 + 4 Ga → 3 Ga2O

Gallium(I) oxide is a strong reducing agent, capable of reducing sulfuric acid to hydrogen sulfide.

Gallium attacks most other metals by diffusing into their metal lattice. Aluminium is highly susceptible, as well as zinc, aluminium-zinc alloys, certain steel grades[1], making them very brittle.


Gallium is a soft silvery metal, brittle at low temperatures. If it is held in the human hand long enough, gallium will melt, since its melting point is 29.76 °C. Gallium expands by 3.1% when it solidifies, and therefore storage in either glass or metal containers should be avoided. Liquid gallium has a strong tendency to supercool below its melting point/freezing point. Unlike mercury, liquid gallium wets glass and skin, making it mechanically more difficult to handle. For this reason, as well as the metal contamination and freezing-expansion problems, samples of gallium metal are usually supplied in polyethylene packets within other containers.


LED's contain a minute amount of gallium nitride, but the quantity is too small to be of importance. Certain low melting alloys contain gallium.

The best source of metallic gallium is GalliumSource, that sells gallium samples, a 100 g sample costs around 65$, though the price does not include shipping. For international shipping, the price is higher and the shipping is included in the price.


Gallium can be prepared by reducing its halides.


  • Inducing embrittlement in susceptible metals, such as aluminium
  • Gallium nitride synthesis
  • Gallium spoon prank
  • Gallium beating heart
  • Hydrogen generation



Pure gallium has little toxicity, but its tendency to wet most materials can be frustrating, so gloves should be worn when handling the pure metal, especially since it will melt in the hand if held too long. Some of its compounds have been shown to cause renal problems in tested animals. Bulk gallium nitride has been shown to be non-toxic and even bio-compatible.[2]


Because gallium tends to expand when it solidifies, it's best stored in thick polyethylene bottles or if it's a small sample, in top lid boxes.


Gallium is best recycled, when possible.



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