Structure
Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.
Measured values
Every bar shows where gallium sits among all 118 elements for that property.
Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.
Size, to scale
Radius 135 pm — that is 0.135 nm, so about 3704 million of them side by side would span a millimetre.
Thermal range
Gallium is liquid over a 2370 K window, from 303 K to 2673 K.
The story
Gallium is the amazing metal that melts in your hand but can survive extreme cold. This silvery-blue post-transition metal has one of the most unusual properties in the periodic table - it melts at just 29.8°C (85.6°F), which means it turns into a shiny liquid puddle when you hold it. But here's the really weird part: liquid gallium can stay liquid down to -120°C if it's pure enough, making it one of the few metals with such an enormous liquid range. Discovered in 1875 by French chemist Paul-Émile Lecoq de Boisbaudran, gallium was actually predicted by Dmitri Mendeleev in 1871 and called "eka-aluminum." When Lecoq found it, the properties matched Mendeleev's predictions almost perfectly, providing spectacular proof that the periodic table was real. The name comes from "Gallia," the Latin name for France. What makes gallium absolutely significant is its role in modern electronics. Gallium arsenide (GaAs) semiconductors are faster and more efficient than silicon, making them essential for high-frequency applications like cell phone amplifiers, satellite communications, and LED lights. Your smartphone probably contains multiple gallium compounds that enable it to transmit data at lightning speeds. Gallium also has some mind-bending properties. It's one of the few substances that expands when it solidifies (like water forming ice), which means solid gallium floats on liquid gallium. It can also wet glass and other materials, creating a mirror-like coating that's being researched for flexible electronics and liquid metal antennas. Here's something incredible: gallium is being researched for cancer treatment. Gallium compounds can interfere with iron metabolism in cancer cells, potentially starving tumors of the iron they need to grow. It's also used in medical imaging as gallium-67, which accumulates in areas of infection and inflammation.
Gallium has a fascinating discovery story that spans several decades and involves multiple scientists, beginning with Dmitri Mendeleev's remarkable prediction and culminating in Paul-Émile Lecoq de Boisbaudran's actual isolation of the element. In 1871, Mendeleev predicted the existence of an unknown element he called "eka-aluminum" based on gaps in his periodic table, accurately forecasting its atomic weight, density, and chemical properties with extraordinary precision. Mendeleev predicted this element would have an atomic weight of about 68, a low melting point, and would form compounds similar to aluminum, properties that would later prove remarkably accurate. The actual discovery occurred in 1875 when French chemist Paul-Émile Lecoq de Boisbaudran was conducting spectroscopic analysis of zinc ore from the Pyrenees Mountains. While examining the spectrum, he noticed two unusual violet lines that did not correspond to any known element, indicating the presence of a new element. Lecoq de Boisbaudran named the element "gallium" after Gallia, the Latin name for France, though some sources suggest it was also a play on his own name (Lecoq meaning "the rooster" in French, and gallus meaning "rooster" in Latin). Within months of the spectroscopic discovery, Lecoq de Boisbaudran successfully isolated a small sample of metallic gallium through electrolysis, confirming its physical properties. The correspondence between Mendeleev's predictions and the actual properties of gallium provided spectacular validation of the periodic law and Mendeleev's periodic table. This discovery became one of the most celebrated examples of scientific prediction in chemistry, demonstrating the predictive power of the periodic system. Lecoq de Boisbaudran's meticulous work in isolating and characterizing gallium established many of its fundamental properties and chemical behaviors that remain accurate today.
Applications
Gallium has become an essential element in modern technology, particularly in the semiconductor and electronics industries. Its primary use is in the production of gallium arsenide (GaAs) and gallium nitride (GaN) semiconductors, which are crucial for high-frequency applications, LED lighting, laser diodes, and solar cells. These semiconductors offer superior performance compared to traditional silicon-based components, especially in high-power and high-frequency applications. Gallium is extensively used in manufacturing blue and white LEDs, which have revolutionized energy-efficient lighting systems worldwide. The metal's unique property of expanding when it solidifies makes it valuable in specialized applications such as dental amalgam alternatives and low-melting-point alloys. In the medical field, gallium compounds are used in radiopharmaceuticals for bone scanning and cancer detection. Gallium-67 citrate is particularly important in nuclear medicine for detecting inflammation and infections. The element also finds applications in thermometers designed for high-temperature measurements, mirrors, and specialized glass compositions. Recent developments have seen gallium being used in advanced photovoltaic cells, where gallium indium phosphide layers improve solar cell efficiency. The aerospace industry utilizes gallium alloys in specialized components that require materials with specific thermal properties. Research continues into gallium's potential applications in quantum computing, where gallium arsenide quantum dots show promise for quantum information processing. The electronics industry relies heavily on gallium for manufacturing high-electron-mobility transistors (HEMTs) used in satellite communications, radar systems, and wireless base stations.
The most common application of gallium is in semiconductor manufacturing, where it forms the backbone of gallium arsenide (GaAs) chips used in smartphones, tablets, and wireless communication devices. Every modern LED light bulb contains gallium nitride, making it one of the most widely distributed elements in consumer products today. Solar panels increasingly incorporate gallium compounds to enhance their efficiency, particularly in concentrated photovoltaic systems used in large-scale solar installations. Medical imaging facilities use gallium-67 for bone scans and infection detection, making it a routine element in healthcare. High-temperature thermometers in industrial settings often contain gallium due to its wide liquid range and low-toxicity properties compared to mercury. The aerospace industry uses gallium alloys in specialized mirrors and optical components for satellites and space telescopes. Consumer electronics benefit from gallium's properties in power amplifiers for cellular base stations and WiFi routers. Automotive applications include gallium-based semiconductors in electric vehicle charging systems and LED headlights. Research laboratories worldwide use gallium arsenide substrates for experimental electronic devices and quantum research. The renewable energy sector employs gallium in advanced solar cell designs, particularly for space applications where efficiency is paramount. Military and defense applications utilize gallium arsenide in radar systems, electronic warfare equipment, and secure communication devices. Even everyday applications like barcode scanners and DVD players rely on gallium arsenide laser diodes for their operation.
Where it comes from
19 mg/kg of Earth's crust · more abundant than 71% of elements
Gallium is one of the rarest stable elements on Earth, with an average concentration of only 19 parts per million in the Earth's crust, making it rarer than lead but more abundant than gold. Unlike many metals, gallium does not exist in nature as a free element due to its high reactivity. Instead, it occurs as a trace element in various minerals, most commonly in bauxite (aluminum ore), zinc ores, and coal. The element is typically found as a substitute for aluminum in minerals such as diaspore and boehmite within bauxite deposits. Sphalerite, the primary zinc ore, contains gallium concentrations ranging from 10 to 300 parts per million, making zinc refining the primary source of gallium production. Coal deposits often contain gallium, and it becomes concentrated in fly ash during coal combustion, providing an alternative extraction source. Some rare earth minerals like loparite and monazite contain trace amounts of gallium. The element is also found in small quantities in iron and manganese ores. Germanite, a copper sulfide mineral, contains significant gallium concentrations and serves as another extraction source. Ocean water contains extremely low concentrations of gallium, approximately 0.03 parts per billion, making sea water extraction economically unfeasible. Most commercial gallium is obtained as a byproduct of aluminum and zinc production rather than being mined directly. The Bayer process used to refine aluminum from bauxite concentrates gallium in the sodium aluminate solution, from which it can be extracted. China, Germany, Kazakhstan, and Ukraine are the primary producers of gallium, with China dominating global production. The element's scarcity and dependence on other metal production makes it strategically important for technology industries.
Handling
Gallium metal is generally considered safe to handle with basic laboratory precautions, but several important safety considerations must be observed. The pure metal poses minimal acute toxicity risks and is not classified as a dangerous substance under normal handling conditions. However, gallium has an unusual property of adhering strongly to glass and other materials, potentially causing permanent staining or surface damage to laboratory equipment and surfaces. Direct skin contact with metallic gallium should be avoided as it can cause skin irritation and may leave persistent stains that are difficult to remove. The metal has a very low melting point (29.8°C), meaning it will melt in warm hands, potentially causing burns if heated above body temperature. Gallium compounds present more significant hazards than the pure metal, with gallium salts being mildly toxic if ingested in large quantities and potentially causing gastrointestinal irritation. Inhalation of gallium dust or fumes should be prevented through proper ventilation and respiratory protection when necessary. The element's semiconductor compounds, particularly gallium arsenide, require special handling procedures due to the presence of toxic arsenic. Workers in semiconductor manufacturing must follow strict protocols to prevent exposure to gallium arsenide dust or vapors. Disposal of gallium-containing materials requires compliance with local hazardous waste regulations, particularly for electronic components and industrial residues. Long-term exposure studies suggest that gallium accumulation in the body is possible, though acute toxicity is rare. Pregnant women and children should exercise additional caution around gallium compounds. Emergency procedures should include immediate washing with soap and water if skin contact occurs, and medical attention if large quantities are accidentally ingested.
Quick answers
Gallium (symbol Ga) is element 31 on the periodic table, a post-transition metal in period 4, group 13. A metal that melts in your hand at 29.8 degrees C and is the foundation of blue LEDs and 5G radios. At room temperature it is a solid.
[Ar] 3d¹⁰ 4s² 4p¹, giving 4 occupied shells holding 2, 8, 18, 3 electrons respectively. Its outer shell holds 3 electrons, which is what sets its bonding behaviour.Gallium melts at 302.9 K (29.8 °C) and boils at 2673 K (2399.9 °C).
The standard atomic weight of Gallium is 69.723 u. That is a weighted average across its naturally occurring isotopes, which is why it is rarely a whole number.
Gallium has a density of 5.91 g/cm³. Water is 1.0 g/cm³, so a block of gallium is about 5.9× heavier.
Gallium has a Pauling electronegativity of 1.81. The scale runs from 0.70 (francium, the least greedy for electrons) to 3.98 (fluorine, the most). Values in this middle band tend to form covalent rather than strongly ionic bonds.
Gallium was discovered in 1875 by Lecoq de Boisbaudran. It is named after latin Gallia, France.
Gallium makes up about 19 mg/kg of the Earth's crust — uncommon, but not rare.