Krypton ionization energy

Fig. 9c. Photoelectron spectra for argon, krypton, and xenon, excited by the helium resonance line (684 A 21-21 e.v.). Ionization energy increases from left to right within each section (see text).

The abihty of these gases to form true chemical compounds with other atoms is limited to the heavier members of the group, krypton, xenon, and radon, where the first ionization energies are reduced to a level comparable with other chemically active elements. Theoretical studies, however, have indicated that it may be possible to isolate helium derivatives, such as MeBeHe. Many of the compounds are prepared at low temperature and characterized through spectroscopic techniques. More recently, multinuclear NMR has emerged as an extremely useful characterization technique. ... 

Atmospheric pressure photoionization (APPI) is a relatively new technique48-51 but the source design is almost identical to that used for APCI except that the corona discharge needle is replaced by a krypton discharge lamp, which irradiates the hot vaporized plume from the heated nebulizer with photons (10 and 10.6 eV). The mechanism of direct photoionization is quite simple. Where the ionization energy of the molecule is less than the energy of the photon, absorption of a photon is followed by ejection of an electron to form the molecular radical ion M+ (Equation (28)). 

The closed-shell configuration of noble gas atoms Ng does not prevent formation of compounds, either as even, positive oxidation states of xenon, isosteric with iodine complexes (and to a smaller extent by krypton and radon) or functioning as Lewis bases. In condensed matter, Ar, Kr, and Xe form distinct NgCr(CO)j and ArCi(NN)5 complexes. Gaseous noble gas molecular ions, especially HeX and ArX, numerous organo-helium cations, and some neon-containing cations are calculated to be quite stable, and several of them are indeed detected in mass-spectra. The history of Ng chemistry and its relations with the Periodic Table, atomic spectra, and ionization energies, are discussed. 

No krypton compounds appear to be thermodynamically stable, but KrF2 can be made from the elements in an electric discharge at very low temperatures, and a few compounds of the cationic species [KrF]+ and [Kr2F3]+ are also known. As the ionization energy of Kr is higher than that of... 

Atmospheric-pressure photoionization (APPI), which was first applied as an LC-MS interface in 2000, is a relatively new ionization technique. The ionization process is initiated by an ultraviolet lamp (krypton discharge lamp), which emits 10.0 and 10.6 eV photons. Any compounds that have ionization energies below 10 or... 

In this iitstmmetrt, iorrs are generated via electron impact in a low pressure somce using three reagerrt gasesA apors krypton, xenon, and mercury. The atomic reagent iorrs formed Kr+, Xe+, and Hg+ all have different ionization energies (IE) (Kr = 13.997 eV, Xe=12.13 eV, Hg= 10.437 eV) and these differences can be utilized... 

Radon lies on the diagonal of the Periodic Table between the true metals and nonmetals and is classed as a metalloid. As the heaviest and most metallic of the naturally occurring noble gases, radon has the lowest ionization energy of the group (1030 kJ mol ) consequently, it is expected to be the most reactive. The chemistry of radon is, however, less extensive than the chemistries of krypton and xenon and is rendered considerably more difficult because no stable isotopes of this element exist. The inherent radiation hazard that accompanies the intense radioactivity of radon requires tracer level experimentation. Nevertheless, evidence has been obtained that radon forms a difluoride and several complex salts. 

Xenon (Z = 54) was the first noble gas to be chemically combined with another element. Xenon and krypton are present in nearly all of the small number of noble gas compounds known today. Note the ionization energy trend begun with the other noble gases in Figure 11.17. What do these facts suggest about the relative reactivities of the noble gases and the character of noble gas compounds ... 

In this section, we focus exclusively on compounds of xenon because most of the known noble gas compounds contain xenon. A few compounds of krypton, such as Krp2, have been synthesized and well characterized. Radon is expected to form compounds even more readily than xenon, because of its lower ionization energy, but the chemistry of radon is complicated by its radioactivity. 

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