Gallium

Discover the fascinating world of Gallium, a versatile element with remarkable properties and wide-ranging applications. This comprehensive guide dives into Gallium’s unique characteristics, showcasing its role in modern technology, from electronics to high-temperature thermometers. Gallium’s low melting point and ability to alloy with other metals make it invaluable in various industries. Through practical examples, explore how Gallium is transforming innovations and becoming a cornerstone in fields like semiconductors and photovoltaics. Unveil the secrets of Gallium, an element that’s shaping the future of technology and beyond.

What is Gallium?

Gallium is a soft, silvery metallic element that stands out due to its unique properties and extensive range of applications. With the atomic number 31, Gallium is remarkable for its low melting point of approximately 29.76°C (85.57°F), which allows it to melt in the palm of one’s hand. This element does not occur as a free metal in nature but is extracted from minerals like bauxite and sphalerite. Gallium is utilized in various fields, notably in electronics for manufacturing semiconductors, LEDs, and solar panels. Its ability to form alloys with other metals enhances its versatility, making Gallium a critical material in scientific research, medical diagnostics, and the development of innovative technologies.

Gallium Formula

• Formula: Ga
• Composition: Consists of a single gallium atom.
• Bond Type: In its elemental form, gallium does not have bonds as it is a pure element. However, gallium can form covalent or ionic bonds when reacting with other elements.
• Molecular Structure: As a pure element, gallium does not form a molecular structure in the same sense as compounds like H₂. At room temperature, gallium is in a metallic state with a close-packed crystalline structure.
• Electron Sharing: In compounds, gallium typically shares electrons covalently or transfers electrons ionically, depending on the nature of the other element(s) it is bonding with.
• Significance: Gallium is notable for its low melting point (29.76°C or 85.57°F) which is close to room temperature, allowing it to melt in one’s hand. It is also important for its use in semiconductors, particularly gallium arsenide (GaAs) and gallium nitride (GaN).
• Role in Chemistry: Gallium plays a crucial role in the semiconductor industry. It forms a variety of compounds that are essential for electronics, optoelectronics, and photonics, making it a key material in modern technology applications.

Structure of Gallium

Gallium, unlike hydrogen, is a metal with distinctive characteristics, including a low melting point but a very high boiling point, indicating its preference to remain in solid or liquid form under normal conditions. Gallium’s behavior at the atomic and molecular levels is quite different from that of hydrogen due to its position in the periodic table and its metallic nature.

Atomic Level: Each gallium atom (Ga) contains 31 protons in its nucleus and has 31 electrons orbiting around it. The electron configuration of gallium is [Ar] 3d¹⁰ 4s² 4p¹, which means it has three electrons in its outermost shell available for bonding.

Molecular Formation: In its metallic form, gallium does not form molecules like H₂. Instead, gallium atoms are arranged in a crystalline lattice structure when solid. This structure involves the sharing of electrons between many gallium atoms in a metallic bond, which is different from the covalent bonding seen in hydrogen molecules. When melted, gallium becomes a liquid but retains its metallic bonding to some degree, leading to its high density and surface tension even in liquid form.

Gallium’s bonds within its lattice are strong, allowing it to maintain its structure until it reaches its melting point of about 29.76°C (85.57°F). Unlike hydrogen, which is a gas at room temperature, gallium is solid but easily melts into a liquid at a temperature slightly above room temperature. It does not exist naturally as a diatomic gas or in a gaseous state under normal conditions due to its high boiling point of approximately 2204°C (3999°F)

Properties of Gallium

Physical Properties of Gallium

Property	Description
Appearance	Silvery-white and metallic
Atomic Number	31
Atomic Weight	69.723
Melting Point	Approximately 29.76°C (85.57°F)
Boiling Point	Approximately 2204°C (3999°F)
Density	5.904 grams per cubic centimeter at 29.6°C (liquid phase)
State at Room Temperature	Solid, but melts slightly above room temperature
Electron Configuration	[Ar] 3d¹⁰ 4s² 4p¹
Crystal Structure	Orthorhombic at room temperature
Thermal Conductivity	40.6 W/(m·K) at 300 K
Electrical Resistivity	270 nΩ·m at 20°C
Electronegativity	1.81 (Pauling scale)
Standard Atomic Weight	69.723
Phase at STP	Solid
Solubility	Insoluble in water, soluble in acids and alkalis
Common Oxidation States	+3

Chemical Properties of Gallium

Gallium, a metal with unique characteristics, exhibits intriguing chemical behaviors. Here’s an overview of its chemical properties, supported by relevant equations to illustrate its reactivity:

1. State at Room Temperature:
   • Gallium is a soft, silvery metal that is solid at room temperature but melts at slightly above, at 29.76°C (85.57°F).
2. Reaction with Air (Oxidation):
   • Gallium forms a protective layer of gallium oxide (Ga₂O₃) when exposed to air, preventing further oxidation.
   • Equation: 4Ga+3O₂​→2Ga₂​O₃
3. Reaction with Water:
   • Unlike many metals, gallium does not react with water at room temperature.
   • Equation: No reaction under normal conditions.
4. Reaction with Acids:
   • Gallium dissolves in mineral acids, producing gallium(III) ions and hydrogen gas.
   • Equation with Hydrochloric Acid: 2Ga+6HCl→2GaCl₃+3H₂
5. Reaction with Alkalis:
   • Gallium also reacts with alkalis to form gallates.
   • Equation with Sodium Hydroxide: 2Ga+2NaOH+6H₂​O→2Na[Ga(OH)4​]+3H₂
6. Amphoteric Nature:
   • Gallium exhibits amphoteric behavior, meaning it can react with both acids and bases.
   • Acid reaction (as above): 2Ga+6HCl→2GaCl₃​+3H₂
   • Base reaction (as above): 2Ga+2NaOH+6H₂​O→2Na[Ga(OH)₄​]+3H₂
7. Alloy Formation:
   • Gallium readily alloys with most metals, significantly lowering their melting points.
   • Example with Indium and Tin (Galinstan): No specific equation, but gallium forms a eutectic alloy, Galinstan, that is liquid at room temperature.
8. Formation of Gallium Halides:
   • Gallium reacts with halogens to form gallium halides, such as gallium(III) chloride.
   • Equation with Chlorine: 2Ga+₃Cl₂→2GaCl₃

Thermodynamic Properties of Gallium

Property	Value with Unit
Boiling Point	2204 °C
Melting Point	29.76 °C
Critical Temperature	Not Clearly Defined
Critical Pressure	Not Clearly Defined
Heat of Vaporization	256 kJ/mol
Heat of Fusion	5.59 kJ/mol
Specific Heat Capacity (at 25°C)	0.371 J/g·K
Thermal Conductivity	40.6 W/m·K

Material Properties of Gallium

Property	Value with Unit
Density (at 29.76 °C)	6095 kg/m³
Viscosity (near m.p.)	1.81 mPa·s
Solubility in Water	Insoluble
Color	Silvery
Phase at Room Temperature	Solid (melts slightly above room temp)

Electromagnetic Properties of Gallium

Property	Value with Unit
Electrical Resistivity (at 20°C)	270 nΩ·m
Thermal Conductivity	40.6 W/m·K
Magnetic Susceptibility	-0.081 × 10^-6 cm^3/mol
Electronegativity (Pauling scale)	1.81

Nuclear Properties of Gallium

Property	Value with Unit
Atomic Number	31
Atomic Mass	69.723 amu
Isotopes	^69Ga (60.1%), ^71Ga (39.9%)
Nuclear Spin (for ^69Ga)	3/2 ℏ
Nuclear Spin (for ^71Ga)	3/2 ℏ
Neutron Cross Section (for ^69Ga)	2.18 barns
Neutron Cross Section (for ^71Ga)	3.6 barns
Nuclear Magnetic Moment (for ^69Ga)	2.0165 µN
Nuclear Magnetic Moment (for ^71Ga)	2.562 µN

Preparation of Gallium

The preparation of gallium primarily involves extracting it from its ores since it does not occur in free form due to its reactive nature. The most common method of gallium production is through the processing of bauxite ore, which is also the principal source of aluminum. Another source is the sphalerite ore, from which zinc is produced. Here’s an overview of the steps involved in the preparation of gallium:

From Bauxite Ore:

1. Extraction of Alumina: Bauxite ore is first processed to extract alumina (Aluminum oxide, Al2O3) through the Bayer process. In this process, bauxite is dissolved in sodium hydroxide (NaOH), which allows for the separation of alumina from the ore.
2. Electrolytic Reduction: The alumina is then subjected to an electrolytic reduction process in a solution of cryolite (Na3AlF6), which is the Hall-Héroult process for aluminum production. Gallium is not the primary product of this process but is found in trace amounts within the aluminum that is produced.
3. Gallium Recovery: The gallium is recovered from this process through an additional electrolysis step or by treating the electrolyte solution with a solvent that extracts the gallium. The solution containing gallium is then subjected to further purification processes, such as electrolysis or crystallization, to obtain pure gallium.

From Sphalerite Ore:

1. Zinc Production: When processing sphalerite ore (ZnS) for zinc, gallium is found as a byproduct. The ore is roasted in the presence of oxygen to convert zinc sulfide to zinc oxide.
2. Leaching and Purification: The zinc oxide is then leached, usually with sulfuric acid, which also dissolves gallium. The solution undergoes purification steps to remove impurities, leaving a solution of gallium sulfate or other gallium salts.
3. Electrolytic Refining: Finally, gallium is obtained through electrolytic refining of the gallium salts, which yields high-purity gallium metal.

Purification:

Regardless of the source, the gallium obtained from these processes may still contain impurities. Further purification is often required, which can be achieved through zone refining. This process involves melting a small section of a long bar of impure metal and slowly moving it along the bar. The impurities concentrate in the melted region and are moved along with the zone, leaving behind a length of purified gallium.

The purified gallium is then solidified and prepared for commercial or industrial use, depending on the required purity level. Gallium’s unique properties, particularly its low melting point and ability to form alloys, make it valuable in various applications, including electronics and high-temperature thermometers.

Chemical Compounds of Gallium

Gallium forms a variety of chemical compounds, many of which are significant in industrial applications, especially in electronics and optics. Below are some notable gallium compounds:

1. Gallium Arsenide (GaAs)

• Equation: Ga + As → GaAs
• Composition: 1 Gallium (Ga), 1 Arsenic (As)
• Properties: Crystalline, direct bandgap
• Uses: Semiconductors, solar cells, IR LEDs

2. Gallium Nitride (GaN)

• Equation: Ga + N₂ → GaN
• Composition: 1 Gallium (Ga), 1 Nitrogen (N)
• Properties: Wide bandgap, high thermal conductivity
• Uses: LEDs, high-power transistors, chargers

3. Gallium Phosphide (GaP)

• Equation: Ga + P → GaP
• Composition: 1 Gallium (Ga), 1 Phosphorus (P)
• Properties: Indirect bandgap
• Uses: Red, orange, green LEDs, photodetectors

4. Gallium Sulfide (GaS)

• Equation: 2Ga + S₂ → 2GaS
• Composition: 2 Gallium (Ga), 1 Sulfur (S)
• Properties: Layered structure
• Uses: Electronics, photonics

5. Gallium Selenide (GaSe)

• Equation: Ga + Se → GaSe
• Composition: 1 Gallium (Ga), 1 Selenium (Se)
• Properties: Layered, hexagonal, nonlinear optics
• Uses: Nonlinear optics, terahertz radiation

6. Gallium Oxide (Ga₂O₃)

• Equation: 4Ga + 3O₂ → 2Ga₂O₃
• Composition: 2 Gallium (Ga), 3 Oxygen (O)
• Properties: Transparent, wide bandgap
• Uses: Power electronics, UV photodetectors

7. Gallium Antimonide (GaSb)

• Equation: Ga + Sb → GaSb
• Composition: 1 Gallium (Ga), 1 Antimony (Sb)
• Properties: Direct bandgap
• Uses: Infrared detectors, LEDs

These compounds of gallium are pivotal in the development of advanced materials and technologies, underscoring the element’s versatility and importance in modern science and engineering

Isotopes of Gallium

Gallium has two naturally occurring isotopes, gallium-69 (^(69)Ga) and gallium-71 (^(71)Ga), with distinct properties and applications in various fields. Here’s a brief overview of these isotopes:

Gallium, primarily has two stable isotopes which are significant in both natural occurrence and practical applications. Here’s an overview of these isotopes, similar to the format used for hydrogen:

Isotope	Symbol	Protons	Neutrons	Natural Abundance	Atomic Mass	Common Uses
Gallium-69	⁶⁹Ga	31	38	~60.1%	68.925	Electronics, semiconductors, NMR spectroscopy
Gallium-71	⁷¹Ga	31	40	~39.9%	70.924	Electronics, semiconductors, neutrino detection

Uses of Gallium

Gallium is a versatile metal with a wide range of applications, owing to its unique properties such as a low melting point, ability to alloy with other metals, and semiconductor characteristics. Here are some of the primary uses of gallium:

1. Electronics and Semiconductors

• Gallium Arsenide (GaAs): Used in the production of high-speed integrated circuits, microwave frequency integrated circuits, solar cells, and infrared light-emitting diodes. It offers superior speed, efficiency, and resistance to radiation compared to silicon.
• Gallium Nitride (GaN): Utilized in light-emitting diodes (LEDs), high-frequency transistors, and power electronics. GaN is known for its high thermal conductivity, power efficiency, and ability to operate at higher temperatures.

2. Photovoltaics:

Gallium is crucial in the production of photovoltaic cells, particularly those made from GaAs, which are highly efficient at converting sunlight into electricity. These cells are used in space applications and in concentrated solar power installations due to their high efficiency and durability.

3. Medical Applications:

Gallium isotopes are used in radiopharmaceuticals for medical imaging and diagnostics. Gallium-67, for example, is used in gallium scans to detect infections and tumors.

4. Thermometers and High-Temperature Gauges:

Due to its unusual melting point (29.76°C), gallium is used in high-precision thermometers and thermal gauges, especially for temperatures close to its melting point.

5. Alloy Production:

Gallium can easily alloy with other metals, and these alloys have a variety of applications. For example, alloys of gallium, indium, and tin (known as Galinstan) have a low melting point and are used as mercury replacements in thermometers, barometers, and other devices.

6. Optical Applications:

Compounds of gallium, like gallium selenide (GaSe), are used in nonlinear optics for frequency doubling, parametric oscillation, and other applications that require the generation of coherent light at different frequencies.

7. Research and Development:

Gallium’s unique properties make it a subject of ongoing research for new applications, including advanced materials and nanotechnology. Gallium liquid metal alloys are being explored for use in flexible electronics and self-healing circuits.

8. Neutrino Detection:

Gallium-71 is used in neutrino detectors for astrophysical research. It has the ability to capture neutrinos, allowing scientists to study solar and cosmic phenomena.

Gallium’s role in technology and science is expansive and continues to grow as new applications for this remarkable metal are discovered. Its contributions to electronics, renewable energy, and medical diagnostics underscore its importance in modern technology and research.

Production of Gallium

Gallium is not found in its elemental form in nature but is extracted as a byproduct of the processing of other metals, notably aluminum and zinc. The primary sources of gallium are the bauxite ore used in aluminum production and the sphalerite ore for zinc. Here’s a simplified overview of the production process:

1. Extraction from Bauxite Ore: During the Bayer process for refining bauxite to produce alumina (Aluminum oxide, Al2O3), gallium accumulates in the caustic liquor that remains after the alumina is precipitated out. Gallium is then extracted from this liquor through a series of chemical treatments and electrolysis.
2. Extraction from Sphalerite Ore: When zinc is produced from sphalerite (ZnS), gallium is found in the byproducts and is extracted through similar chemical processes involving leaching, precipitation, and electrolysis.
3. Purification: The gallium extracted through these methods is further purified through processes like zone refining, which involves melting a small section of a long bar of impure gallium and slowly moving it along the bar. The impurities are concentrated in the melt and moved to one end of the bar, leaving behind purified gallium.

Applications of Gallium

Gallium’s unique physical and chemical properties enable its use in a variety of high-tech applications:

1. Semiconductors: Gallium’s most significant application is in the semiconductor industry. Gallium arsenide (GaAs) and gallium nitride (GaN) are used in integrated circuits, microwave frequency integrated circuits, and light-emitting diodes (LEDs) because they offer advantages over silicon in speed, efficiency, and thermal stability.
2. Photovoltaics: Gallium arsenide is also used in highly efficient photovoltaic cells for solar panels, particularly in space applications where efficiency and durability are crucial.
3. Optoelectronics: GaN and GaAs are essential for optoelectronic devices, including laser diodes used in optical storage devices, fiber optic communication systems, and infrared light applications.
4. Medical Applications: Radioactive isotopes of gallium, such as gallium-67, are used in nuclear medicine for diagnosing and imaging of various diseases, including cancer and infections.
5. Thermometers: Gallium alloys, which have a low melting point, are used in high-temperature thermometers and are considered a non-toxic alternative to mercury thermometers.
6. Metal Alloys: Gallium can easily alloy with metals like indium and tin to create alloys with low melting points, useful in applications like medical thermometers, high-temperature switches, and in some cooling systems.
7. Research and Development: Gallium’s unusual properties, such as its ability to remain liquid over a wide temperature range and its non-toxicity, make it an area of interest for research in materials science, particularly for flexible electronics and liquid metal batteries

Can gallium Destroy Metal?

Gallium can weaken or damage certain metals like aluminum by infiltrating the grain boundaries, leading to structural failure without technically “destroying” the metal.

Is gallium safe to touch?

Yes, gallium is safe to touch. It is considered to have low toxicity, but prolonged skin contact should be avoided to prevent potential irritation.

Gallium, with its unique low melting point and applications in semiconductors, plays a critical role in modern technology. Safe for handling, its use in electronics, medicine, and research underscores its versatility and growing importance in advancing innovative solutions.