Valence Shell Ionization Energy

The diagonal elements of the HF-LCAO matrix are taken to be the negatives of the valence shell ionization energy for the orbital in question. These can be determined from a study of atomic spectra. 

TABLE 14. Valence-shell ionization energies (eV) for polyatomic ER2, E = Ge, Sn, Pb... 

BH3 is an important small molecule for which experimental data are lacking, since it readily dimerizes to BsHe. Several earlier papers were devoted to this question, particularly studies by Kutzelnigg and co-workers, who562 estimated from IEPA calculations that the dimerization energy is 151 +21 kJ mol-1. BHa was also studied in SCF calculations some years ago by Schwartz and Allen,583 who considered the inner-shell and valence-shell ionization energies. More recently, Goddard and Blint have discussed GVB wavefunctions for BH3.155... 

Table 3.1. First ionization energies lEl, valence shell s electron ionization energies lE(nr), and mean valence shell ionization energies MIE (all in kJ mol ) of the first 20 elements.

Configuration-averaged ionization energies and mean valence shell ionization energies... 

Allen [3] has defined the mean valence shell ionization energy or MIF of an atom as the weighted mean of the configuration-averaged ionization energies of valence shell 5 and p electrons ... 

Fig. 3.3. The mean valence shell ionization energies, ME, and A-H bond distances in hydrogen compounds of main group elements (Group 18 elements excluded). The numbers on the perpendicular axis refer to MIEs in kJ mol multiplied by 10 and to bond distances i (A-H) in pm. The experimental bond distances have been taken from the gaseous, monomeric compounds AH,. AH,. AH,. AH2, AH4, AH3, AH2 and HA of the elements in Groups 1, 2, 12, 13, 14, 15, 16 and 17 respectively. Note that bond distances for. GaH2,. InH2 and. TIH2 are missing.

Table 3.2. Mean valence shell ionization energies MIE coefficients x of elements in Gronps 1, 2, and 12 throngh...

Allen has suggested that the electronegativity coefficient x should be defined in terms of the mean valence shell ionization energy [3] ... 

Mean valence shell ionization energies MIE (in kJ mol ) and Allen electronegativity coefficients / of elements in Groups 1,2, and 12 through 18. 

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