Gallium (Ga) is a chemical element with an atomic number of 31 in the periodic table of elements. It mainly occurs as a part of the chemical compounds found in Earth’s crust, in a quantity of 0.0005%.
This chemical substance is a member of the boron family (group 13), which includes the semi-metal boron (B) and the metals aluminum (Al), indium (In), and thallium (Tl). Just like them, gallium is also a trivalent element with an atomic radius of 130 pm that participates in numerous compounds with the other chemicals. Its most common oxidation state is +3.
Chemical and Physical Properties of Gallium
| Property | Value |
| Name: | Gallium |
| Symbol: | Ga |
| Atomic Number: | 31 |
| Atomic Weight: | 69.723 g.mol-1 |
| Group Number: | 13 (Post-transition metals) |
| Period: | 4 |
| Color: | A lustrous, silvery-white metal with a bluish hue |
| Physical State: | Solid at room temperature |
| Density: | 5.907 g/cm³ |
| Melting Point: | 302.93 K |
| Boiling Point: | 2253 K |
| Group: | Metal |
| Shells: | 2,8,18,3 |
| Valence: | 2,3 |
| Crystal Structure: | Orthorhombic |
| Electro Negativity: | 1.81 |
| Covalent Radius: | 1.26 Å |
| Atomic Radius: | 1.81 Å |
| Atomic Volume: | 11.8 cm³/mol |
| Name Origin: | Latin: Gallia (France) |
| Discovered By: | Paul Émile Lecoq de Boisbaudran |
| Year: | 1875 |
| Location: | France |
| Pronunciation: | GAL-i-em |
| Uses: | Used in semiconductor production. It is used in making LEDs (light-emitting diodes) and GaAs laser diodes. |
| Description: | Grayish-white metal |
With the periodic table symbol (Ga), atomic number 31, atomic mass of 69.72 g.mol-1, and electron configuration [Ar] 3d104s24p1, gallium is a soft and corrosive post-transition metal that reaches its boiling point at 2229°C (4044°F, 2502 K).
The low melting point of this element is achieved at 29.7646°C (85.5763°F, 302.9146 K), which triggers the melting of gallium even at (or rather, close to) room temperature. Liquid gallium is difficult to work with, since it tends to stick to surfaces, such as glass, skin, etc. Due to this, Ga cannot be stored in glass or metal containers.
The pure elemental form of gallium has an orthorhombic crystal structure. It adopts a solid aggregate condition at room temperature but liquifies when exposed to higher temperatures. Gallium shares this property with the elements mercury, caesium, and rubidium that also turn from solid substances to a liquid state upon heating.
Similar to mercury, the pure gallium metal is characterized by a stunning lustrous silvery color with a bright, highly reflective surface.
Gallium is classified in the group of post-transition metals, along with aluminum, indium and thallium, tin, lead, and bismuth. It readily reacts with acids and alkalis but is stable in reactions with air and molecules of water. The low density of this chemical allows gallium to expand when exposed to low temperatures, which is a property it shares with water.
How Was Gallium Discovered?
The story of gallium’s discovery begins in Paris, in 1875. That year, the French chemist Paul-Émile Lecoq de Boisbaudran (also known as François Lecoq de Boisbaudran) performed a chemical analysis of a sample of zinc blende ore (ZnS) obtained from the Pyrenees.
Upon a closer look at the isolated zinc from the sample, de Boisbaudran noticed a new violet line in the atomic spectrum of the substance under his observation. This evidence was pointing to a new, undiscovered chemical element.
In fact, it was the element named “eka-aluminum” predicted by Dmitri Mendeleev. According to his scientific estimations, this chemical was supposed to occupy the place in the periodic table under the chemical element aluminum (Al) according to its chemical properties. The great Russian chemist even came close to the atomic mass of this element, by predicting around 68 g.mol-1 for the gallium element.
However, de Boisbaudran succeeded in isolating the pure elemental form of gallium by conducting electrolysis of gallium hydroxide in potassium hydroxide solution. He also managed to determine its properties by comparing it to the chemical element aluminum, after which this French chemist presented his scientific findings to the French Academy of Sciences as the discoverer of the new chemical element – gallium (Ga).
How Did Gallium Get Its Name?
The name of this chemical element was derived from the Latin word for France, the home country of the chemist Paul-Émile Lecoq de Boisbaudran who discovered gallium. In fact, there is a double symbolism behind the name of gallium. Namely, ‘Gallia’ (gaul) in Latin refers to the European country France, but gallium is also a reference to the name of its discoverer (Lecoq) that in Latin translates as ‘gallus’, or ‘a rooster’.
Where Can You Find Gallium?
What makes this chemical element a bit more different than the rest is the fact that gallium is not mined from mineral ore since it is found only in trace amounts in them. Rarely occurring in its free elemental form in nature, gallium is mostly derived as a by-product of mining and the processing of iron pyrites, zinc blende, diaspore, germanite, and bauxite (aluminum), and copper.
As an impurity, gallium is mostly contained in coal, bauxite, and the mineral sphalerite. In addition, gallite is the most common form of a mineral from which the crude gallium feedstock can be obtained.
France, along with Germany and Japan, is among the countries that are the largest producers of refined gallium. On the other hand, the most used gallium compounds in the United States are gallium arsenide (GaAs) and gallium nitride (GaN).
Gallium in Everyday Life
Regarding its chemical properties, gallium is mostly used in the metal and electronics industry. However, its most significant use is in medicine, or more specifically, in radiology. The following is a list of the most common gallium uses in the everyday life:
- The gamma-emitting isotope gallium-67 is used in gallium scan diagnostics in medicine;
- Due to its ability to convert electricity to light, gallium is used in the manufacturing of red LEDs (light-emitting diodes);
- As a semiconductor, gallium nitride is applied in in Blu-ray technology, manufacturing of blue and green LEDs, transistors, and pressure sensors for touch switches, as well as in mobile phones;
- Gallium finds use in the production of semiconductor compounds as a liquid metal ion source for a focused ion beam;
- The gallium arsenide compound (GaAs) is found to be an excellent replacement for silicone; it also has a wide application in the production of high-power infrared laser diodes, optoelectronic devices, solar-powered cars, and space probes due to its ability to convert electricity directly into coherent light;
- When added to metal alloys, gallium makes them more brittle;
- Gallium trichloride is used by the Neutrino Observatory in Italy to study solar neutrinos produced in the Sun;
- The high boiling point of gallium is a property exploited in the production of high-temperature thermometers, since it makes this substance ideal for recording temperatures.
Gallium Scans
After platinum, gallium is the second-most administered metal ion in the treatment therapy of cancer patients. In nuclear medicine, gallium is often applied as one of the key substances in the cancer treatment procedures, such as PET (positron emission tomography) scans, bone scans, MUGA (multigated acquisition) scans, and gallium scans.
The latter radiographic procedure, the gallium scan, makes use of the gallium-67 radioactive isotope as a tracer for the imaging of soft bodily tissues in cancer patients. The gallium scan can be used for the detection of cancerogenic tumors suspected in every part of the body, but, principally, it is applied for the detection of tumors that attack the lymphatic system of the body.
How Dangerous Is Gallium?
Gallium is a trace element found in extremely small quantities in the human body. It’s generally considered to be mildly toxic. However, some of the gallium compounds impose a greater risk of adverse health effects.
Since this chemical substance is a strong calcium resorption inhibitor, it is administered in the treatment of high calcium levels in the blood caused by cancer. It’s also used as a tracer in gallium scans, but the radiation emitted during this radiological test can be compared to the more common x-ray examinations, and is also quickly eliminated from the body.
However, larger quantities of gallium that accumulate in the body by the long term use of gallium-based medicines may increase the risk of kidney dysfunctionality. According to the National Library of Medicine, long exposure to gallium may even lead to tumor fibrosis.
Environmental Effects of Gallium
Since gallium is present only in small amounts in its elemental form in Earth’s crust, it does not pose a great risk for the environment. However, nowadays, gallium is used largely in the metal and electronic industries as well as in medicine.
In turn, the industrial waste containing gallium may cause environmental issues, such as gallium contamination, pollution, and adverse health effects due to exposure to high levels of this chemical element.
Isotopes of Gallium
Gallium-69 and gallium-71 are the two stable isotopes that make the pure elemental form of galium – 31Ga. With a half-life of 3.3 days, gallium-67 is the longest living form of this chemical element which is standardly used in gallium scans.
| Nuclide
[n 1] | Z | N | Isotopic mass (Da)
[n 2][n 3] | Half-life | Decay
mode [n 4] | Daughter
isotope [n 5] | Spin and
parity [n 6][n 7] | Natural abundance (mole fraction) | |
| Excitation energy | Normal proportion | Range of variation | |||||||
| 56Ga | 31 | 25 | 55.99491(28)# | p | 55Zn | 3+# | |||
| 57Ga | 31 | 26 | 56.98293(28)# | p | 56Zn | 1/2−# | |||
| 58Ga | 31 | 27 | 57.97425(23)# | p | 57Zn | 2+# | |||
| 59Ga | 31 | 28 | 58.96337(18)# | p | 58Zn | 3/2−# | |||
| 60Ga | 31 | 29 | 59.95706(12)# | 70(10) ms | β+ | 60Zn | (2+) | ||
| 61Ga | 31 | 30 | 60.94945(6) | 168(3) ms | β+ | 61Zn | 3/2− | ||
| 62Ga | 31 | 31 | 61.944175(30) | 116.18(4) ms | β+ | 62Zn | 0+ | ||
| 63Ga | 31 | 32 | 62.9392942(14) | 32.4(5) s | β+ | 63Zn | (3/2−) | ||
| 64Ga | 31 | 33 | 63.9368387(22) | 2.627(12) min | β+ | 64Zn | 0(+#) | ||
| 65Ga | 31 | 34 | 64.9327348(9) | 15.2(2) min | β+ | 65Zn | 3/2− | ||
| 66Ga | 31 | 35 | 65.931589(3) | 9.49(7) h | β+ | 66Zn | 0+ | ||
| 67Ga[n 8] | 31 | 36 | 66.9282017(14) | 3.2612(6) d | EC | 67Zn | 3/2− | ||
| 68Ga[n 9] | 31 | 37 | 67.9279801(16) | 67.71(9) min | β+ | 68Zn | 1+ | ||
| 69Ga | 31 | 38 | 68.9255736(13) | Stable | 3/2− | 0.60108(9) | |||
| 70Ga | 31 | 39 | 69.9260220(13) | 21.14(3) min | β− (99.59) | 70Ge | 1+ | ||
| EC (0.41%) | 70Zn | ||||||||
| 71Ga | 31 | 40 | 70.9247013(11) | Stable | 3/2− | 0.39892(9) | |||
| 72Ga | 31 | 41 | 71.9263663(11) | 14.095(3) h | β− | 72Ge | 3- | ||
| 73Ga | 31 | 42 | 72.9251747(18) | 4.86(3) h | β− | 73Ge | 3/2− | ||
| 74Ga | 31 | 43 | 73.926946(4) | 8.12(12) min | β− | 74Ge | (3-) | ||
| 75Ga | 31 | 44 | 74.9265002(26) | 126(2) s | β− | 75Ge | (3/2)− | ||
| 76Ga | 31 | 45 | 75.9288276(21) | 32.6(6) s | β− | 76Ge | (2+,3+) | ||
| 77Ga | 31 | 46 | 76.9291543(26) | 13.2(2) s | β− | 77Ge | (3/2−) | ||
| 78Ga | 31 | 47 | 77.9316082(26) | 5.09(5) s | β− | 78Ge | (3+) | ||
| 79Ga | 31 | 48 | 78.93289(11) | 2.847(3) s | β− (99.911%) | 79mGe | (3/2−)# | ||
| β−, n (.089%) | 78Ge | ||||||||
| 80Ga | 31 | 49 | 79.93652(13) | 1.697(11) s | β− (99.11%) | 80Ge | (3) | ||
| β−, n (.89%) | 79Ge | ||||||||
| 81Ga | 31 | 50 | 80.93775(21) | 1.217(5) s | β− (88.11%) | 81mGe | (5/2−) | ||
| β−, n (11.89%) | 80Ge | ||||||||
| 82Ga | 31 | 51 | 81.94299(32)# | 0.599(2) s | β− (78.5%) | 82Ge | (1,2,3) | ||
| β−, n (21.5%) | 81Ge | ||||||||
| 83Ga | 31 | 52 | 82.94698(32)# | 308(1) ms | β− (60%) | 83Ge | 3/2−# | ||
| β−, n (40%) | 82Ge | ||||||||
| 84Ga | 31 | 53 | 83.95265(43)# | 0.085(10) s | β−, n (70%) | 83Ge | |||
| β− (30%) | 84Ge | ||||||||
| 85Ga | 31 | 54 | 84.95700(54)# | 50# ms [>300 ns] | 3/2−# | ||||
| 86Ga | 31 | 55 | 85.96312(86)# | 30# ms [>300 ns] | |||||
Source: Wikipedia
List of Gallium Compounds
Having a trivalent electron configuration, gallium most often forms oxides, hydrides, fluorides, chlorides, bromides, sulphides, selenides, tellurides, and nitrides:
- Gallium acetylacetonate
- Gallium antimonide
- Gallium arsenide
- Gallium arsenide phosphide
- Gallium maltolate
- Gallium nitrate
- Gallium nitride
- Gallium phosphate
- Gallium phosphide
- Gallium selenide
- Gallium trichloride
- Gallium(I) oxide
- Gallium(II) selenide
- Gallium(II) sulfide
- Gallium(II) telluride
- Gallium(III) bromide
- Gallium(III) fluoride
- Gallium(III) hydroxide
- Gallium(III) iodide
- Gallium(III) oxide
- Gallium(III) selenide
- Gallium(III) sulfide
- Gallium(III) telluride
- Triethylgallium
- Trimethylgallium
- Gallium(III) NitriteGa
- Gallium Sulfite
- Gallium(III) Carbonate
- Gallium(III) Sulfate Octadecahydrate
- Gallium(III) Cyanide
- Gallium(III) Oxide
- Gallium Trichloride
- Gallium(III) Nitride
- Gallium(III) Acetate
- Gallium(III) Sulfate
- Gallium(III) Orthophosphate
- Gallium(III) Hydrogen Sulfate
- Gallium(III) Hydroxide
- Gallium(III) Arsenide
- Gallium(III) Sulfide
- Gallium(II) Peroxide
- Gallium(III) Dichromate
- Gallium(III) Perchlorate
- Gallium(II) Chloride
- Gallium Oxalate
5 Interesting Facts and Explanations
- Gallium arsenide was one of the main elements used in the solar panels on the Mars Exploration Rover.
- Paul-Émile Lecoq de Boisbaudran was one of the pioneers of spectroscopy. His great contribution is seen in the improvement of the spectroscopic techniques used in contemporary chemical analysis.
- This alkaline earth metal is the 32nd most abundant element found in the Earth’s crust.
- Compared to the other metal elements of the periodic table, gallium has the largest liquid range of all since it remains in liquid state until the temperature reaches 4000°F (2204°C). Even the temperature of our hands can melt this chemical element. Gallium is also one of the few elements with higher density in the liquid state, thus belonging to the group composed of water, silicon, germanium, antimony, bismuth, and plutonium.
- Gallium-67 and gallium-68 are the most commercially exploited radioactive gallium isotopes.