|Boiling Point: 119.95°K, -153.2°C,
Melting Point: 115.93°K, -157.22°C, -251°F
Electrons Energy Level: 2, 8, 18, 8
Isotopes: 20 + 6 Stable
Heat of Vaporization: 9.029 kJ/mol
Heat of Fusion: 1.638 kJ/mol
Density: 3.75 g/L @ 273°K & 1atm
Specific Heat: 0.248 J/g°K
Atomic Radius: 1.03Å
Ionic Radius: unknown
Electronegativity: N/A (Pauling); 2.94 (Allrod Rochow)
|Krypton (Greek, ???pt??
meaning "hidden") is neither green
nor a solid material that can defeat Superman. It was discovered in Great
Britain, 1898 by Sir William Ramsay and Morris Travers in residue left from evaporating
nearly all components of liquid air. It ranks sixth in abundance in
the atmosphere. Krypton gas is used in various kinds of lights, from small bright
flashlight bulbs to special strobe lights for airport runways.
Krypton is characterized by a brilliant red and orange spectral signature. It is one of the products of uranium fission. Solidified krypton is white and crystalline with a face-centered cubic crystal structure which is a common property of all "rare gases".
As with the other noble gases, krypton is isolated from the air by liquefaction.
In 1960 an international agreement defined the meter in terms of light emitted from a krypton isotope. One of the naturally occurring non-radioactive isotopes of krypton, Kr-86 (17.3%) was used as the basis for the international definition of the meter. One meter was 1,650,762.73 wavelengths of the red-orange spectral line of krypton-86. This agreement replaced the longstanding standard meter located in Paris which was a metal bar made of a Platinum-iridium alloy (the bar was originally estimated to be one ten millionth of a quadrant of the earth's polar circumference). But only 23 years later, the Krypton-based standard was replaced itself by the speed of lightthe most reliable constant in the universe. In October 1983 the Bureau International des Poids et Mesures (International Bureau of Weights and Measures) defined the meter as the distance that light travels in a vacuum during 1/299,792,458 seconds.
1s2 2s2p6 3s2p6d10 4s2p6
The concentration of krypton in earth's atmosphere is about 1 ppm. It can be extracted from liquid air by fractional distillation. Once thought to be completely inert, krypton is known to form a few compounds. Krypton difluoride (KrF2) is the easiest krypton compound to make and gram amounts of it have been produced.
Like the other noble gases, krypton is widely considered to be chemically inert. Following the first successful synthesis of xenon compounds in 1962, synthesis of krypton difluoride was reported in 1963. Other fluorides and a salt of a krypton oxoacid have also been found. ArK+ and KrH+ molecule ions have been investigated and there is evidence for KrXe or KrXe+.
At the University of Helsinki in Finland, HKrCN and HKrCCH (krypton hydride-cyanide and hydrokryptoacetylene) were synthesized and determined to be stable up to 40oK.
There are 20 known isotopes of krypton. Naturally occurring krypton is made of six stable and one slightly radioactive isotope. Krypton's spectral signature is easily produced with some very sharp lines. 81Kr is the product of atmospheric reactions with the other naturally occurring isotopes of krypton. It is radioactive with a half-life of 250,000 years. Like xenon, krypton is highly volatile when it is near surface waters and 81Kr has therefore been used for dating old (50,000 - 800,000 year) groundwater. 85Kr is an inert radioactive noble gas with a half-life of 10.76 years, that is produced by fission of uranium and plutonium. Sources have included nuclear bomb testing, nuclear reactors, and the release of 85Kr during the reprocessing of fuel rods from nuclear reactors. A strong gradient exists between the northern and southern hemispheres where concentrations at the North Pole are approximately 30% higher than the South Pole due to the fact that most 85Kr is produced in the northern hemisphere, and north-south atmospheric mixing is relatively slow.
The high cost of obtaining krypton from the air has limited its practical applications. Krypton is used in some types of photographic flashes used in high speed photography. Some fluorescent light bulbs are filled with a mixture of krypton and argon gases. Krypton gas is also combined with other gases to make luminous signs that glow with a greenish-yellow light. In 1960, the length of the meter was defined in terms of the orange-red spectral line of krypton-86, an isotope of krypton. Argon gases are mixed with Krypton to create a special kind of fluorescent light bulb.
Krypton Fluoride Laser
One major use of krypton is the krypton fluoride laser. Certain amounts of energy are added to force krypton gas to react with fluorine gas to become KrF excited state complex.
The compound will decompose once the energy supply stops. During the decomposition process, the excess energy stored in the excited state complex will be emitted in the form of strong ultraviolet laser radiation.
Atomic Radius (Å): 1.03Å
Electrochemical Equivalents: unknown
Atomic Mass Average: 83.8
(Gr. kryptos, hidden) Discovered in 1898 by Ramsay and Travers in the residue left after liquid air had nearly boiled away. Krypton is present in the air to the extent of about 1 ppm. The atmosphere of Mars has been found to contain 0.3 ppm of krypton. It is one of the "noble" gases. It is characterized by its brilliant green and orange spectral lines. Naturally occurring krypton contains six stable isotopes. Seventeen other unstable isotopes are now recognized. The spectral lines of krypton are easily produced and some are very sharp. In 1960 it was internationally agreed that the fundamental unit of length, the meter, should be defined in terms of the orange-red spectral line of 86Kr. This replaced the standard meter of Paris, which was defined in terms of a bar made of a platinum-iridium alloy. In October 1983 the meter, which originally was defined as being one ten millionth of a quadrant of the earth's polar circumference, was again redefined by the International Bureau of Weights and Measures as being the length of a path traveled by light in a vacuum during a time interval of 1/299,792,458 of a second. Solid krypton is a white crystalline substance with a face-centered cubic structure which is common to all the "rare gases." While krypton is generally thought of as a rare gas that normally does not combine with other elements to form compounds, it now appears that the existence of some krypton compounds is established. Krypton difluoride has been prepared in gram quantities and can be made by several methods. A higher fluoride of krypton and a salt of an oxyacid of krypton also have been reported. Molecule-ions of ArKr+ and KrH+ have been identified and investigated, and evidence is provided for the formation of KrXe or KrXe+. Krypton clathrates have been prepared with hydroquinone and phenol. 85Kr has found recent application in chemical analysis. By imbedding the isotope in various solids, kryptonates are formed. The activity of these kryptonates is sensitive to chemical reactions at the surface. Estimates of the concentration of reactants are therefore made possible. Krypton is used in certain photographic flash lamps for high-speed photography. Uses thus far have been limited because of its high cost. Krypton gas presently costs about $30/l.
Source: CRC Handbook of Chemistry and Physics, 1913-1995. David R. Lide, Editor in Chief. Author: C.R. Hammond