Ionization energy table solutes

The standard reduction potentials for the M /M couples (Table 13.1) show that Al (aq) is much less readily reduced in aqueous solution than are the later ions. This can be attributed, in part, to the more negative Gibbs energy of hydration of the smaller Al ion. However, an important contributing factor (scheme 13.71) in differentiating between the values of for the Al /Al and Ga /Ga couples is the significant increase in the sum of the first three ionization energies (Table 13.1). 

The decrease in ionization energy in solution is due to the effect of I1 which is always greater than I Vq I. If the same solute is measured in different hydrocarbons, approximately the same polarization energy should result, since is approximately 2 for most of the hydrocarbons. In Table 5, the polarization energies of the positive anthracene ion in three different solvents are given. A value of -1.06 eV is obtained for all three solvents which is an indication that the anion radius is constant, since Er is approximately the same for the three liquids. 

Table 5.1 lists some of the atomic properties of the Group 2 elements. Comparison with the data for Group 1 elements (p. 75) shows the substantial increase in the ionization energies this is related to their smaller size and higher nuclear charge, and is particularly notable for Be. Indeed, the ionic radius of Be is purely a notional figure since no compounds are known in which uncoordinated Be has a 2- - charge. In aqueous solutions the reduction potential of... 

Let us apply these ideas to the third-row elements. On the left side of the table we have the metallic reducing agents sodium and magnesium, which we already know have small affinity for electrons, since they have low ionization energies and are readily oxidized. It is not surprising, then, that the hydroxides of these elements, NaOH and Mg(OH)z, are solid ionic compounds made up of hydroxide ions and metal ions. Sodium hydroxide is very soluble in water and its solutions are alkaline due to the presence of the OH- ion. Sodium hydroxide is a strong base. Magnesium hydroxide, Mg(OH)2, is not very soluble in water, but it does dissolve in acid solutions because of the reaction... 

The availability of the electron pair in the isolated ligand can be directly measmed by photoelectron spectroscopy. The comparative ionization potentials show a reverse of the proton aftrnities in aqueous systems. For example, the gas-phase basicity of PPhs (lower ionization energy) is greater than that of PMc3 a selection of values is given in Table 6. These differences between solution based gas-phase basicities are ascribed to solvation effects. 

The effect of solvation on the IPs of nucleotides has been investigated by Le-Breton and coworkers using a combination of photoelectron spectroscopy and computational methods. They conclude that the first and second ionization potentials of the nucleotides deoxycytidine 5 -phosphate (CMP) and deoxythymidine 5 -phosphate (TMP) arise from ionization of the negatively charged phosphate group and nucleobase, respectively, both in the gas phase and in solution. The difference in the calculated first and second ionization potentials is smaller for the hydrated versus gas phase nucleosides as a consequence of the larger solvation energy for the zwit-terion formed upon ionization of the nucleobase versus the neutral radical formed upon ionization of the phosphate. The calculated adiabatic ionization potentials for the hydrated nucleobases CMP and TMP are 5.8 and 6.0 eV, respectively, considerably lower than the gas phase nucleobase ionization potentials (Table 1). 

To our knowledge, 46 has never been observed in solution under stable conditions, even at low temperature. Pulse radiolysis " of benzyl chloride as well as flash photolysis ° of several derivatives in HHP have allowed the observation of the electronic absorption spectra of benzyl and its 4-methyl and 4-methoxy derivatives. The and NMR spectra of the 2,4,6-trimethylbenzyl cation and other more heavily substituted benzyl cations, however, have been studied at low temperature in superacid media. In the gas phase, cold benzyl radical has been probed by two-color, resonant two-photon ionization techniques, thus providing very accurate vibrational frequencies below 650 cm for the benzyl cation. Furthermore, the adiabatic ionization energy of benzyl radical and several isotopomers in the ground state were determined from their threshold photoionization spectra using resonant two-photon excitation and detection of electrons by pulsed field ionization. This information, combined with Af//° (CgH5CH2) from Ref. 212 leads to the value of Af//°m(46) reported in Table 9. 

Sources Data from Ionization energies cited in this chapter are from C. E. Moore, Ionization Potentials and Ionization Limits Derived fwm the Analyses of Optical Spectra, National Standard Reference Data Series, U.S. National Bureau of Standards, NSRDS-NBS 34, Washington, DC, 1970, unless noted otherwise. Electron affinity values listed in this chapter are from H. Hotop and W. C. Lineberger, J. Phys. Chem. Ref Data, 1985,14, 731. Standard electrode potentials listed in this chapter are from A. J. Bard, R. Parsons, and J. Jordan, eds., Standard Potentials in Aqueous Solutions, Marcel Dekker (for lUPAC), New York, 1985. Electronegativities cited in fiiis chapter are from J. B. Mann, T. L. Meek, and L. C. Allen, J. Am. Chem. Soc., 2000,122, 2780, Table 2. Other data are from N. N. Greenwood and A. Earnshaw, Chemistry ofthe Elements, Pergamon Press, Elmsford, NY, 1984, except where noted. J. Emsley, The Elements, Oxford University Press, New York, 1989. S. G. Bratsch, J. Chem. Educ., 1988,65, 34. 

Referring to the periodic table, arrange the atoms Ne, Na, P, Ar, K in order of increasing first ionization energy. SOLUTION... 

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