Quick Facts
| Property | Value |
|---|---|
| Symbol | Ga |
| Atomic Number | 31 |
| Atomic Mass | 69.723 u |
| Category | Post-Transition Metal |
| Period | 4 |
| Group | 13 |
| Block | p |
| Electron Configuration | [Ar] 3d¹⁰ 4s² 4p¹ |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Solid (barely—melts at 29.76°C) |
| Density | 5.91 g/cm³ |
| Melting Point | 29.76°C (302.91 K) |
| Boiling Point | 2204°C (2477 K) |
| Appearance | Silvery-blue metal |
Atomic Properties
| Property | Value |
|---|---|
| Electron Configuration | [Ar] 3d¹⁰ 4s² 4p¹ |
| Electronegativity | 1.81 (Pauling scale) |
| First Ionization Energy | 578.8 kJ/mol |
| Atomic Radius | 135 pm |
| Covalent Radius | 122 pm |
| Van der Waals Radius | 187 pm |
History and Discovery
Discovered by: Paul Emile Lecoq de Boisbaudran Year of Discovery: 1875 Location: Paris, France
Etymology
Named after "Gallia," the Latin name for France. Some suggest it's also a pun on "le coq" (the rooster, gallus in Latin), referring to the discoverer's name.
Discovery Story
Dmitri Mendeleev predicted the existence of "eka-aluminum" in 1871. Paul Emile Lecoq de Boisbaudran discovered gallium in 1875 by spectroscopic analysis of sphalerite ore. The properties matched Mendeleev's predictions remarkably well, providing strong support for the periodic table.
Isotopes
| Isotope | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|
| ⁶⁹Ga | 60.11% | Stable | - |
| ⁷¹Ga | 39.89% | Stable | - |
Occurrence
Natural Abundance
Gallium is relatively rare, comprising about 19 ppm of Earth's crust. It does not occur free in nature and has no primary ore. It is extracted as a byproduct from bauxite (aluminum ore) and sphalerite (zinc ore).
Extraction and Production
- Byproduct: From aluminum and zinc production
- Bayer Process: Gallium extracted from bauxite processing liquors
- Sources: No dedicated gallium mines
- Global production: about 400 tons annually
Applications and Uses
Electronics
- Gallium arsenide (GaAs) semiconductors
- Integrated circuits
- LEDs (light-emitting diodes)
- Solar cells
- Microwave circuits
Specialty Alloys
- Low-melting alloys
- Galinstan (gallium-indium-tin alloy, liquid at room temperature)
- Replacing mercury in thermometers
Medical Applications
- Gallium-67 for medical imaging (gamma camera scans)
- Cancer and infection detection
- Gallium nitrate for hypercalcemia treatment
Other Uses
- High-temperature thermometers
- Neutrino detection
- Wetting agent for porcelain
Biological Role
Gallium has no known biological role in humans or other organisms.
In the Human Body
Gallium is not normally found in the body. Trace amounts may be present from environmental exposure.
Medical Research
Gallium compounds show antimicrobial properties and are being researched for treating infections.
Safety and Hazards
Toxicity
Gallium metal is considered low toxicity. Gallium compounds vary in toxicity. Prolonged skin contact with liquid gallium should be avoided.
Handling Precautions
- Liquid gallium wets skin and can be difficult to remove
- Gallium can alloy with other metals (attacks aluminum)
- Store in glass or plastic containers
- Gallium arsenide is more hazardous due to arsenic content
Environmental Impact
Gallium is rare and production has limited environmental impact. GaAs semiconductor disposal requires proper handling.
Interesting Facts
- Gallium melts just above room temperature—it can melt in your hand
- It has one of the largest liquid ranges of any metal (29.76°C to 2204°C)
- Like water, gallium expands when it solidifies
- Gallium can make aluminum extremely brittle through liquid metal embrittlement
- Gallium was the first new element to confirm Mendeleev's periodic table predictions