Xenon (Xe)
Xenon (Xe) is a colorless and odorless chemical element classified as a noble gas, with an atomic number of 54. Discovered in 1898 by scientists Sir William Ramsay and Morris Travers, xenon was the first noble gas shown to form compounds, challenging the previous belief that noble gases were entirely inert. This element exists in trace amounts in Earth's atmosphere and certain mineral springs, and it has a low density and specific gravity, contributing to its gaseous state at standard conditions. Xenon possesses a variety of stable isotopes, with nine known to occur naturally, and is characterized by weak interatomic forces leading to low melting and boiling points.
Xenon's unique properties have led to several practical applications, particularly in lighting and medicine. The xenon flash lamp, developed in the 1930s, produces bright flashes of light and is widely used in photography and specialized lighting. In medicine, xenon has emerged as an effective general anesthetic and is also utilized in MRI procedures to enhance imaging. Despite its rarity and the necessity for specialized extraction methods, xenon's versatility makes it significant across various fields, including photography, automotive, and healthcare.
Xenon (Xe)
- Element Symbol: Xe
- Atomic Number: 54
- Atomic Mass: 131.293
- Group # in Periodic Table: 18
- Group Name: Noble gases
- Period in Periodic Table: 5
- Block of Periodic Table: p-block
- Discovered by: Sir William Ramsay, Morris W. Travers (1898)
Xenon is a chemical element of the periodic table. It is a member of the noble gas family, which also contains the elements argon, neon, helium, krypton, and radon. Noble gases are only minimally chemically reactive, and they are generally colorless and odorless. The noble gases were once thought to be unable to form compounds, but xenon proved this belief to be wrong, because it was the first in its family to be synthesized into a noble gas compound.
Sir William Ramsay and Morris Travers discovered xenon in 1898 at University College London. The two scientists had just discovered two other noble gas elements, krypton and neon, by extracting them from liquid air. After this discovery, the pair wondered whether any additional gases were contained in liquid air, and upon receiving a donation of new equipment from a wealthy industrialist, they were able to extract more of the gas krypton. They continued distilling this sample until, eventually, a new gas heavier than krypton was isolated. When viewed in a spectrometer, this new gas gave off glowing blue lines. Ramsay and Travers dubbed the new element "xenon," which comes from the Greek word for "stranger." Ramsay went on to receive the Nobel Prize in Chemistry a few years later, in 1904, for his discovery of the three noble gases.
Physical Properties
At 298 kelvins (K), xenon’s standard state is gaseous. In this state, xenon is both colorless and odorless and has a density of 5.761 × 10−3 grams per cubic centimeter (g/cm3). It has a specific gravity of 4.56. The specific gravity of an element is a measurement of its density in comparison with that of water. Xenon, as a noble gas, displays weak interatomic force, which is the force of attraction between neighboring atoms. As a result of this characteristic, both the melting point and boiling point of xenon, like those of the other noble gases, are extremely low. The melting point of xenon is −111.75 degrees Celsius (°C), and its boiling point is −108.099 °C. The specific heat of xenon at a temperature of 20 °C is 158.32 joules per kilogram-kelvin (J/kg·K).
Chemical Properties
Common oxidation states of xenon are +6, +4, +2, and 0. Xenon has thirty-six isotopes with known half-lives, and naturally occurring xenon is made up of nine stable isotopes. Xenon has the largest number of stable isotopes after tin, which has ten, and both are the only elements to have more than seven. Of xenon’s many unstable isotopes, xenon-136 has the longest half-life, at 2.11 × 1021 years. Unstable xenon isotopes undergo beta decay, which is a form of radioactive decay in which a proton is converted into a neutron (or vice versa) inside the nucleus of an atom; when the atom goes through this process, energy is released in the form of a beta particle (a fast-moving electron or positron), usually resulting in a white, blue, or lavender flash. Xenon has a close-packed, cubic crystal structure.
Until the mid-twentieth century, noble gases were thought to be incapable of forming compounds with other elements due to their very minimal chemical reactivity, and they were therefore referred to as "inert gases." However, Neil Bartlett proved this theory to be untrue in 1962 when he successfully synthesized the first noble-gas compound, xenon hexafluoroplatinate. Since Bartlett’s discovery, many more noble-gas compounds have been formed, usually by compounding with platinum, oxygen, and fluorine.
Applications
Xenon is a rare gas, but it can be found in Earth’s atmosphere in small amounts—approximately 0.086 parts per million by volume, which is the same amount of xenon that is found in the atmosphere of Mars. In addition, xenon can be found in the gases emitted by certain mineral springs found on Earth. Naturally occurring xenon is not considered to be toxic to humans, and it is only when it is compounded with other elements that toxicity becomes an issue. In order to extract xenon from natural sources, equipment that can distill the element from liquid air is required.
In the 1930s, Harold Edgerton, an American engineer, began experimenting with xenon while aiming to develop strobe-light technologies for photographic purposes. He found that xenon gas, when excited by electrical currents, emits a very bright, white flash of light. He soon invented the xenon flash lamp, which uses this very technique. This technology is commonly used in strobe lights and photography flashes as well as in other lights for specialized purposes, such as the arc lamps that are used to project motion pictures. In addition, xenon is used in fog lights on some vehicles that require extra illumination, as well as in bright lamps for deep-sea missions. Xenon provides a brighter, more illuminating light than traditional lighting techniques.
Xenon also has various uses in the field of medicine. It has been found to be an effective, though expensive, form of general anesthetic. The more common anesthetic nitrous oxide, better known as laughing gas, is a greenhouse gas, making it unfriendly to the environment when it is released back into the atmosphere. By contrast, not only is xenon a more effective anesthetic than nitrous oxide, but when it is vented back out, it is simply returning to the place in the environment from which it was originally sourced. Xenon has also been found to be useful in imaging empty cavities in the body during magnetic resonance imaging (MRI) procedures.
Bibliography
Furgang, Adam. The Noble Gases: Helium, Neon, Argon, Krypton, Xenon, Radon. New York: Rosen, 2010. Print.
Haynes, William M., ed. CRC Handbook of Chemistry and Physics. 95th ed. Boca Raton: CRC, 2014. Print.
"Noble Gases." Kirk-Othmer Encyclopedia of Chemical Technology. 5th ed. Vol. 17. Hoboken: Wiley, 2007. Print.
Schrobilgen, Gary J. "Xenon (Xe)." Encyclopaedia Britannica. Encyclopaedia Britannica, 2015. Web. 30 July 2015.
"Technical Data for Xenon." The Photographic Periodic Table of the Elements. Element Collection, n.d. Web. 30 July 2015.