Xenon ionization energy

The stability of the electronic configuration is indicated by the fact that each element has the highest ionization energy in its period, though the value decreases down the group as a result of increasing size of the atoms. For the heavier elements is it actually smaller than for first-row elements such as O and F with consequences for the chemical reactivities of the noble gases which will be considered in the next section. Nuclear properties, particularly for xenon, have been exploited for nmr spectroscopy and Mdssbauer... 

Heats of formation for a complete set of Group VILA fluorides are unavailable, but a set of xenon fluoride cations, isoelectronic with iodine fluorides, exhibits the alternating pattern expected for odd- and even-electron molecules. The original energy-level diagram for stepwise fluorine dissociation is shown in Fig. 5. The tabulated values were derived from the ionization energies of XeF and the threshold values for XeFJ — XeF, - + F, where n is even (27), together with heats of formation obtained by reaction calorimetry (137). 

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 mercury atom is smaller than expected from the zinc-cadmium trend and is more difficult to ionize than the lighter atoms. In consequence the metal-metal bonding in mercury is relatively poor, resulting in the element being a liquid in its standard state. This almost Group 18 behaviour of mercury may be compared to that of a real Group 18 element, xenon, which has first and second ionization energies of 1170 and 2050 kJ mol. ... 

Xc obviously will have a fairly high electron affinity (sec the ionization energy of atomic xenon], and ifit gains an electron, it will dissociate (sec Chapters). Combine these facts with the choice of SbF as solvent and dCNl-tr.ise theory to provide a self-consistent interpretation. 

Isoelectronic in a formal sense, but quite different in the energies involved is the Xe ion believed to exist in certain very acidic solvents (see Chapter 17). The energetics of the situation are not completely understood, but presumably the much lower ionization energy of xenon can more readily be compensated by the solvation energy of the polar solvent, thus stabilizing the Xe cation. 

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. ... 

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. 

With their closed-shell electron configurations the noble gas elements of group 18 were long regarded as chemically inert. However, in 1962 Bartlett noted that the ionization energy of xenon was similar to that of 02, and by reaction with PtF6 attempted to prepare the compound analogous to... 

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