Krypton

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. Solid krypton is a white crystalline substance with a face-centered cubic structure, which is common to all the rare gases.  

It is one of the noble gases. It is characterized by its brilliant green and orange spectral lines. 

Krypton clathrates (an inclusion complex in which molecules of one substance are completely enclosed within the other) 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. 

From the Greek word, xenon, meaning stranger. Discovered by Ramsay and Travers in 1898 in the residue left after evaporating liquid air components, xenon is a member of the noble, or inert, gases. It is present in the atmosphere to the extent of about one part in 20 million. Xenon is present in the Martian atmosphere to the extent of 

08 ppm. The element is also found in the gases evolved from certain mineral springs, and is commercially obtained by extraction from liquid air. 

Krypton is an inert, nontoxic, colorless, odorless gas that can act as a simple asphyxiant if it displaces the air needed to support life. It is normally shipped as a gas. The gas is much heavier than air (sp. gr. = 2.82). 

If liquid krypton contacts the skin, flush the affected area with water. If extensive burns result, contact a physician. 

If a person has lost consciousness, remove him to an open space (use self-contained breathing apparatus if necessary), apply artificial respiration, and then call for medical aid. 

All fluid handling and transfer operations should be conducted in well-ventilated areas by two or more persons. 

Use a face shield and protective clothing to avoid contact with the fluid. 

ATOMIC MASS 83.798 amu VALENCE 0 and 2 OXIDATION STATE 0 NATURAL STATE Gas 

ORIGIN OF NAME The name krypton is derived from the Greek word kryptos, meaning hidden.  

ISOTOPES There are a total of 37 isotopes of krypton. Six of these are stable Kr-78, Kr-80, Kr-82, Kr-83, Kr-84, and Kr-86. The isotope Kr-78 has such a long half-life (0.9x1 years) that it is considered stable even though it contributes only 0.35% to the natural krypton in the Earth s atmosphere. All the others are radioactive, man-made by-products of nuclear power plants and radioactive isotopes with half-lives ranging from 107 nanoseconds to 2.29x 10+ years. 

Krypton is a rather dense, tasteless, colorless, odorless gas. Its critical temperature is between that of oxygen and carbon dioxide. It is extracted during fractional distillation of liquid oxygen at a temperature of about -63.8°C. At one time it was thought that krypton, as well as the other noble gases, were completely inert. However, in 1967 scientists were able to combine fluorine with krypton at low temperatures to form the compound krypton difluoride (KrFj). In this case krypton has a valence of 2. 

Kryptons melting point is —156.6°C, its boiling point is —152.30°C, and its density is 0.003733g/cm3. 

Lactic acid (2-hydroxypropionic acid, CH3CH0HC02H, boiling point 122°C, melting point 18°C, density 1.2060) is one of the oldest known organic acids. It is the primary acid constituent of sour milk and is formed by the fermentation of milk sugar (lactose) by Streptococcus lactis. 

Commercially, lactic acid is manufactured by controlled fermentation of the hexose sugars from molasses, corn, or milk. Lactates are made by synthetic methods from acetaldehyde and lactonitrile, a by-product acrylonitrile production. 

References [1] Busemann et al. (2000) [2] Huss and Lewis (1994b), renormalized following Busemaim et al. (2000) [3] Lewis et al. (1994), [4] Gdbel et al. (1978), avg. of 7 ureilites, except for (ureilite Kenna WiUcening and Marti 1976). [5] Crabb and Anders (1981), South Oman. 

Besides neon, xenon has turned out to be the element most diagnostic in its isotopic composition. An important role has been played by Xenon-HL, which was the first of the nucleosynthetic isotope anomalies to be discovered (Reynolds and Turner 1964). The HL component has received its name for the simultaneous overabundance of the heavy xenon isotopes (= Xe-H) and the light xenon isotopes (= Xe-L). Because the H part originally was more reliably determined, Xenon-HL was first believed to be associated with fission, possibly of a superheavy element (e.g., Anders et al. 1975), but in the end the search for its host phase led to the discovery of the existence of grains of presolar origin in primitive meteorites (Lewis et al. 1987). 

Compositions are listed in Table 5. Again, as in the case of Kr, Xe-HL as listed is based on mixing lines, assuming Xe/ Xe in the HL component to have a value of 

which is close to the most extreme measured value and the intersection of the P3-HL and P6-HL mixing lines (Huss and Lewis 1994b). To derive the other end composition of the mixing line observed in the low-temperature release, which corresponds to Xe-P3, a Ae/ Xe ratio of -0.310, just below the lowest measured value was assumed (Table 5 Huss and Lewis 1994b). Again, for P6, the component with which Xe-HL mixes at higher release temperature two compositions are listed, based on two different (normal vs. exotic) assumptions for Xe/ Xe in it. 

The compositions of Xe-G and Xe-N present in presolar SiC and graphite grains—in analogy to Kr—have been partitioned based on mixing lines and theoretical guidelines. 

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Make the following approximate calculations for the surface energy per square centimeter of solid krypton (nearest-neighbor distance 3.97 A), and compare your results with those of Table VII-1. (a) Make the calculations for (100), (110), and (111) planes, considering only nearest-neighbor interactions, (b) Make the calculation for (100) planes, considering all interactions within a radius defined by the sum... 

Another indication of the probable incorrectness of the pressure melting explanation is that the variation of the coefficient of friction with temperature for ice is much the same for other solids, such as solid krypton and carbon dioxide [16] and benzophenone and nitrobenzene [4]. In these cases the density of the solid is greater than that of the liquid, so the drop in as the melting point is approached cannot be due to pressure melting. 

Substances in this category include Krypton, sodium chloride, and diamond, as examples, and it is not surprising that differences in detail as to frictional behavior do occur. The softer solids tend to obey Amontons law with /i values in the normal range of 0.5-1.0, provided they are not too near their melting points. Ionic crystals, such as sodium chloride, tend to show irreversible surface damage, in the form of cracks, owing to their brittleness, but still tend to obey Amontons law. This suggests that the area of contact is mainly determined by plastic flow rather than by elastic deformation. 

Fig. XVII-18. Contours of constant adsorption energy for a krypton atom over the basal plane of graphite. The carbon atoms are at the centers of the dotted triangular regions. The rhombuses show the unit cells for the graphite lattice and for the commensurate adatom lattice. (From Ref. 8. Reprinted with permission from American Chemical Society, copyright 1993.)...

Fender B E F and Halsey G D Jr 1962 Second virial coefficients of argon, krypton and argon-krypton mixtures at low temperatures J. Chem. Phys. 36 1881... 

Such isothemis are shown in figure B 1,26.4 for the physical adsorption of krypton and argon on graphitized carbon black at 77 K [13] and are examples of type VI isothemis (figure B 1.26.3 ). Equation (B1.26.7)) further... 

Figure Bl.26.4. The adsorption of argon and krypton on graphitized carbon black at 77 K (Eggers D F Jr, Gregory N W, Halsey G D Jr and Rabinovitch B S 1964 Physical Chemistry (New York Wiley) eh 18).

Nitrogen is the most widely used absorbent (at 77 K) for the BET method and has been employed almost universally. Argon is more suited to the measurement of microporous zeolites. Krypton may be used for the... 

Krypton is found to be an extremely unreactive element indicating that it has a stable electronic configuration despite the fact that the n = 4 quantum le el can accommodate 24 more electrons in the d and / orbitals. 

It also forms compounds known as carbonyls with many metals. The best known is nickel tetracarbonyl, Ni(CO)4, a volatile liquid, clearly covalent. Here, donation of two electrons by each carbon atom brings the nickel valency shell up to that of krypton (28 -E 4 x 2) the structure may be written Ni( <- 0=0)4. (The actual structure is more accurately represented as a resonance hybrid of Ni( <- 0=0)4 and Ni(=C=0)4 with the valency shell of nickel further expanded.) Nickel tetracarbonyl has a tetrahedral configuration,... 

Heliurn, neon, argon, krypton, xenon, radon)... 

Following Bartlett s discovery of xenon hexafluoroplatinate(VI), xenon and fluorine were found to combine to give several volatile, essentially covalent fluorides, and at least one fluoride of krypton has been obtained. From the xenon fluorides, compounds containing xenon-oxygen bonds have been made much of the known chemistry of xenon is set out in Figure 12.1. 

The O oxidation state is known in vanadium hexacarbonyl. V(CO)(,. a blue-green, sublimable solid. In the molecule VfCO), if each CO molecule is assumed to donate two electrons to the vanadium atom, the latter is still one electron short of the next noble gas configuration (krypton) the compound is therefore paramagnetic, and is easily reduced to form [VfCO, )]. giving it the... 

One hypothesis says that fluorine can be substituted for hydrogen wherever it occurs in organic compounds, which could lead to an astronomical number of new fluorine compounds. Compounds of fluorine with rare gases have now been confirmed in fluorides of xenon, radon, and krypton. 

Argon is two and one half times as soluble in water as nitrogen, having about the same solubility as oxygen. Argon is colorless and odorless, both as a gas and liquid. Argon is considered to be a very inert gas and is not known to form true chemical compounds, as do krypton, xenon, and radon. 

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. 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... 

It is the most corrosion-resistant metal known, and was used in making the standard meter bar of Paris, which is a 90 percent platinum and 10 percent iridium alloy. This meter bar was replaced in 1960 as a fundamental unit of length (see under Krypton). 

Krypton-85 has been used for over 25 years to measure the density of paper as it is amanufactured. The total weight of paper can be controlled to a very accurate degree by the use of krypton 85 and other radioactive nuclides. The common name for such a device is a beta gague that can measure the thickness of a material. 

Noble gases (Section 1 1) The elements in group VIIIA of the penodic table (helium neon argon krypton xenon radon)... 

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