- Xenon (Xe) is a noble gas with atomic number 54, positioned in Group 18 of the periodic table alongside helium, neon, argon, krypton, and radon.
- At standard conditions, xenon is a colorless, odorless, and tasteless gas that is chemically inert under most circumstances.
- It has a complete outer electron shell with eight valence electrons in the 5s and 5p subshells, giving it exceptional stability. Its atomic structure consists of fifty-four protons, typically seventy-seven or seventy-eight neutrons, and fifty-four electrons arranged in five shells.
- Naturally occurring xenon is composed of nine stable isotopes, with xenon-132 (¹³²Xe) being the most abundant at about 26.91%. Several xenon isotopes, such as xenon-124 (¹²⁴Xe) and xenon-136 (¹³⁶Xe), are very weakly radioactive with extremely long half-lives.
- Xenon is rare in the Earth’s atmosphere, with an average concentration of only 0.087 parts per million by volume. It is obtained commercially by fractional distillation of liquefied air, where it is separated along with krypton in the final stages. Small amounts of xenon are also found in certain minerals and natural gas deposits.
- The element was discovered in 1898 by British chemists Sir William Ramsay and Morris Travers, who were investigating the components of liquefied air after removing nitrogen, oxygen, argon, and other gases. They identified xenon in the residual fraction as a heavy gas that produced a bright blue glow in a vacuum discharge tube. The name “xenon” comes from the Greek xenos, meaning “stranger” or “foreigner,” reflecting its rarity.
- In modern applications, xenon is used in specialized lighting, electronics, and medicine. Xenon gas is employed in high-intensity discharge lamps, strobe lights, and lighthouse beacons due to its bright white light. In projection systems and film projectors, xenon arc lamps provide a daylight-like spectrum. Xenon is also used in ion propulsion systems for spacecraft, where its high atomic mass makes it an efficient propellant for electric thrusters. In medicine, xenon is valued as a non-toxic, fast-acting general anesthetic and is used in imaging techniques such as xenon-enhanced computed tomography (CT) to measure blood flow.
- Chemically, xenon was long thought to be completely inert, but in 1962, Neil Bartlett demonstrated that it could form compounds with highly electronegative elements like fluorine. Since then, several xenon compounds have been synthesized, including xenon hexafluoroplatinate (XePtF₆), xenon difluoride (XeF₂), xenon tetrafluoride (XeF₄), and xenon hexafluoride (XeF₆). Xenon oxides, such as xenon trioxide (XeO₃) and xenon tetroxide (XeO₄), are powerful oxidizing agents.
- Biologically, xenon has no known essential role in humans or other organisms. It is chemically inert and non-toxic, though at high pressures it can cause narcosis, similar to nitrogen. In medical settings, xenon’s anesthetic properties are advantageous because it is not metabolized and does not harm organ systems.
- From an environmental perspective, xenon is not considered a pollutant, as it is inert and present only in trace amounts in the atmosphere. However, radioactive xenon isotopes are produced in nuclear fission reactions and can serve as indicators of nuclear activity, making them important in monitoring nuclear test ban treaty compliance.
