We continue to review some of the most important materials in heat treatment and metallurgy.
Xenon (chemical symbol: Xe)
Xenon (Fig. 1) is a rare, colorless, odorless, tasteless gas and (contrary to most people’s understanding) inert with respect to most (but not all) chemicals. Xenon is very dense, having a density approximately 4.5 times that of air (at sea level), and is considered a trace element within the Earth’s atmosphere to the extent of about 1 part in 20 million. Despite the tendency for noble gases to resist forming bonds with other elements, xenon was the first in which a chemical reaction was synthesized by scientists in the creation of xenon hexafluoroplatinate (XePtF6). Since then, a number of xenon compounds have been made, typically with fluorine and oxygen – for instance, xenon trioxide (XeO3) and xenon tetroxide (XeO4), which are both highly explosive solids.
Xenon was first discovered in 1898 by British chemists William Ramsay and Morris Travers (Fig. 2), who had previously worked together in discovering the noble gases of krypton and neon. Their discovery came when they analyzed the residue that remained after evaporating components of liquid air and viewing these remnants through spectroscopic analysis. The analysis showed blue lines that had previously been unseen, indicating the presence of a new element. They named their latest discovery xenon, derived from the Greek word “xenos” meaning stranger.
Xenon sees a wide range of uses today spanning a number of different industries. In the photography industry, xenon is used for photographic flashes, as well as high-pressure arc lamps for both motion-picture projection and to produce ultraviolet light. Sunbed lamps utilize xenon gas within electrical discharge tubes to give their iconic blue glow (Fig. 3). In the medical industry, it sees use within instruments used for medical imaging, radiation detection (i.e., neutron and X-ray counters), bactericidal lamps, certain chemotherapy medication and even as a general anesthetic. A recent use of xenon is within modern ion thrusters used for both space travel and for the movement of satellites. In this application, the xenon gas is used as a propellant to minimize the risk of explosions associated with chemical propulsion.
Here are a few important facts about Xenon.
- Atomic number: 54
- Atomic weight: 131.293
- Melting point: 161.36 K (-111.79°C or -169.22°F)
- Boiling point: 165.03 K (-108.12°C or -162.62°F)
- Density: 0.005887 grams per cubic centimeter
- Phase at room temperature: Gas
- Element classification: Nonmetal
- Period number: 5
- Group number: 18
- Group name: Noble gas
- Electron configuration: [Kr] 4d105s25p6