Quick Facts
| Property | Value |
|---|---|
| Symbol | Xe |
| Atomic Number | 54 |
| Atomic Mass | 131.29 u |
| Category | Noble Gas |
| Period | 5 |
| Group | 18 |
| Block | p |
| Electron Configuration | [Kr] 4d¹⁰ 5s² 5p⁶ |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Gas |
| Density | 0.005887 g/cm³ |
| Melting Point | -111.75°C (161.40 K) |
| Boiling Point | -108.09°C (165.06 K) |
| Appearance | Colorless gas (blue glow in discharge) |
Atomic Properties
| Property | Value |
|---|---|
| Electron Configuration | [Kr] 4d¹⁰ 5s² 5p⁶ |
| Electronegativity | 2.6 (Pauling scale) |
| First Ionization Energy | 1170.4 kJ/mol |
| Atomic Radius | 108 pm |
| Covalent Radius | 140 pm |
| Van der Waals Radius | 216 pm |
History and Discovery
Discovered by: William Ramsay and Morris Travers Year of Discovery: 1898 Location: London, England
Etymology
Named from the Greek "xenos" meaning "stranger" or "foreign," because it was a stranger in the atmosphere.
Discovery Story
William Ramsay and Morris Travers discovered xenon in 1898, shortly after discovering krypton and neon. They isolated it by fractionally distilling liquid air and identified it by its unique spectrum. It was the last of the stable noble gases to be discovered.
Isotopes
| Isotope | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|
| ¹²⁴Xe | 0.095% | Stable | - |
| ¹²⁶Xe | 0.089% | Stable | - |
| ¹²⁸Xe | 1.910% | Stable | - |
| ¹²⁹Xe | 26.401% | Stable | - |
| ¹³⁰Xe | 4.071% | Stable | - |
| ¹³¹Xe | 21.232% | Stable | - |
| ¹³²Xe | 26.909% | Stable | - |
| ¹³⁴Xe | 10.436% | Stable | - |
| ¹³⁶Xe | 8.857% | 2.2 × 10²¹ years | β⁻β⁻ |
Occurrence
Natural Abundance
Xenon is extremely rare, comprising only about 0.087 ppm of Earth's atmosphere. It is the rarest non-radioactive noble gas. Mars has a higher proportion of atmospheric xenon than Earth.
Extraction and Production
- Fractional Distillation of Air: Only commercial source
- Byproduct: From liquid air separation
- Very Limited: Due to extreme rarity
- Global production: about 40 tons annually
Applications and Uses
Lighting
- High-intensity discharge lamps (car headlights)
- Arc lamps for movie projectors
- Flash lamps
- Xenon short-arc lamps
Medical Applications
- General anesthesia (experimental)
- Medical imaging
- Neuroprotection research
- Lung imaging (hyperpolarized xenon)
Space Technology
- Ion propulsion systems
- Satellite thrusters
- NASA's Dawn mission used xenon ion engines
Other Uses
- Nuclear magnetic resonance (NMR)
- Excimer lasers
- Dark matter detection experiments
- Window insulation (high-performance)
Biological Role
Xenon has no biological role but has interesting medical properties as an anesthetic.
In the Human Body
Xenon is not normally present in the body. As an anesthetic, it is quickly eliminated after use.
Medical Properties
Xenon shows neuroprotective properties and is being researched for treating brain injuries. It is an excellent anesthetic but expensive.
Safety and Hazards
Toxicity
Xenon is non-toxic. At high concentrations it acts as an anesthetic, and at very high levels can be an asphyxiant.
Handling Precautions
- Can displace oxygen in confined spaces
- Anesthetic effects at high concentrations
- Compressed gas requires proper handling
- Liquid xenon causes frostbite
Environmental Impact
Xenon is environmentally benign. It does not affect the ozone layer or climate.
Interesting Facts
- Xenon was the first noble gas to form true chemical compounds (1962, XeF₂)
- Xenon anesthesia is considered one of the best—fast onset, rapid recovery, no toxicity
- It is so rare that all the xenon in Earth's atmosphere would fill a cube about 150 meters on a side
- Xenon ion engines provide very efficient thrust for spacecraft
- Neil Bartlett's synthesis of xenon compounds revolutionized chemistry in 1962