Main-group elements electron affinities

After an electron is added to an atom, the "affinity" that it has for the electron is known as the electron affinity. Because energy is released when an electron is added to most atoms, it follows that to remove the electron would require energy, so the quantity is positive for most atoms. The electron affinities for most of the main group elements are shown in Table 1.1. It is useful to remember that 1 eV per atom is equal to 96.48kj/mol. 

The importance of scalar relativistic effects for compounds of transition metals and/or heavy main group elements is well established by now [44], Somewhat surprisingly (at first sight), they may have nontrivial contributions to the TAE of first-row and second-row systems as well, in particular if several polar bonds to a group VI or VII element are involved. For instance, in BF3, S03) and SiF4, scalar relativistic effects reduce TAE by 0.7, 1.2, and 1.9kcal/mol, respectively - quantities which clearly matter even if only chemical accuracy is sought. Likewise, in a benchmark study on the electron affinities of the first-and second-row atoms [45] - where we were able to reproduce the experimental values to... 

Electron affinities for the main group elements. Negative values mean that anions form with the release of energy. Positive values mean that energy is ahsorhed in order to form the anion. The positive values are estimated, because the anions formed for atoms of groups 2 and 18 are unstable. 

As new values were obtained, atomic electron affinities were reviewed periodically beginning in 1953 [1-13]. All the available experimental, extrapolated, and theoretical values were tabulated in 1984 [7]. Presently, experimental values are available at the NIST website [12]. Prior to 1970 the majority of the values for the main group elements were determined by the Born Haber cycle, electron impact, or relative and absolute equilibrium surface ionization techniques. However, values for C, O, and S had been measured by photodetachment [1-3]. By the mid-1970s virtually all the Ea of the main group elements in the first three rows had been measured by photon methods [4-7]. By the early 1980s values were obtained for the transition elements by photon techniques [7, 8]. In the 1990s the values of Ca, Sr, and Ba were measured [9-13]. Recently, experimental values have been reported for Ce, Pr, Tm, and Lu [14-17],... 

Figure 8.3 Plots of the Ea of the main group elements versus the period number to illustrate the consistency of the electron affinities of a given family.

Figure 8.14 Electron affinities of the main-group elements. The electron affinities (in kJ/mol) of the main-group elements are shown. Negative values indicate that energy is released when the anion forms. Positive values, which occur in Group 8A(18), indicate that energy is absorbed to form the anion in fact, these anions are unstable and the values are estimated.

Electron affinities of some main group elements are listed in Table 3.3. Electron affinities are seen to be particularly large for the elements in Groups 16 and 17. The noble gases in Group 18, however, do not form gaseous anions. 

Table 33. The electron affinities (in kJ mol of some main group elements [4]...

The electron affinities (in kJ mol ) of some main group elements. Recommended values for the polarizability volumes a (in 10 m ) of some atoms and monatomic ions in the gas phase. 

Figure 8.13 Electron affinities of the main-group elements (in kJ/mol). Values...

Table 9.4 Electron affinities of main-group elements, EJeV ...

Table 10.2 lists values for the main-group elements. Robert Mulliken proposed an alternative definition in terms of the ionization energy, I, and the electron affinity, ea, of the element expressed in electronvolts ... 

Figure 8.16 displays the electron affinities for a number of main-group elements. As you can see from this figure, the trends in electron affinity are not as regular as trends in other properties we have examined. For instance, we might expect electron affinities to... 

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