Radon ionization energy

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. 

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. 

Using only the periodic table, arrange the following elements in order of increasing ionization energy radon, helium, neon, xenon. 

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. 

Shimo, M., A Flow-Type Ionization Chamber for Measuring Radon Concentration in the Atmospheric Air, in Atmospheric Radon Familiers and Environmental Radioactivity (S. Okada, ed) pp. 37-42, Atomic Energy Society of Japan, Tokyo (1985) (in Japanese). 

The difference in the ionization potentials of xenon and krypton (1170 versus 1351 kj/mol) indicates that krypton should be the less the reactive of the two. Some indication of the difference can be seen from the bond energies, which are 133 kj/mol for the Xe-F bond but only 50 kj/mol for the Kr-F bond. As a result, XeF2 is considerably more stable of the difluorides, and KrF2 is much more reactive. Krypton difluoride has been prepared from the elements, but only at low temperature using electric discharge. When irradiated with ultraviolet light, a mixture of liquid krypton and fluorine reacts to produce KF2. As expected, radon difluoride can be obtained, but because all isotopes of radon undergo rapid decay, there is not much interest in the compound. In this survey of noble gas chemistry, the... 

Early experiments in liquids were quite variable for many reasons. The conductivity technique, which was used in the gas phase to measure dose, was not applicable to the liquid phase. Reactions were measured using dissolved radium salts or radon gas as the ionization source. Some thought the chemistry was due to the reactions with radium however, it was soon recognized that it was the emitted rays that caused the decomposition. Both radium and radon could cause radiation damage. Because the radon would be partitioned between the gas and liquid phase, the amount of energy that was deposited in the liquid depended critically on the experimental conditions such as the pressure and amount of headspace above the liquid. In addition, because the sources were weak, long irradiation times were necessary and products, such as hydrogen peroxide, could decompose. 

Kushneva V. 1959. On the problem of the long-term effects of the combined injury to animals of silicon dioxide and radon. In Zakutinskil D. Long term effects of injuries caused by the action of ionizing radiation. AEC-TR-4473. U.S. Atomic Energy Commission. 

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