Electron affinity of fluorine

Electron affinity of atomic fluorine (in kJ moP 1 eV 96.5 kJ moP ) computed using a variety of theories and basis sets (including spin-orbit correction) 

There is dramatic improvement from the 6-31G(d) to the 6-31 + G(d) basis set. The diffuse functions ( + ) provide the extra room needed by the additional electron in the negative ion. There is a similar improvement from cc-pVTZ to aug-cc-pVTZ for the same reason. Moving to aug-cc-pVQZ has a smaller effect because the additional functions are mostly in the tighter valence region. 

There is also dramatic improvement when correlation is included (i.e., everything in Table 2 besides HF). Correlation is important whenever the number of electron pairs changes, as here. As discussed above, the HF and B3LYP results are less sensitive to the basis set than the post-HF methods (compare the aug-cc-pVTZ and aug-cc-pVQZ results). The strong dependence on both basis set and electron correlation makes EA(F) a difficult quantity to calculate. The most rigorously calculated value yet published is 328.32 kJmol [100], only 0.16 kJmol above the experimental benchmark. 

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Electron affinities are difficult to measure and are known reliably for only a small fraction of the hundred or so elements. The electron affinity of fluorine is one that is known ... 

The neutral fluorine atom has seven valence electrons that is, seven electrons occupy the highest partially filled cluster of energy levels. This cluster of energy levels thus contains one fewer electron than its capacity permits. The electron affinity of fluorine shows that the addition of this last electron is energetically favored. This is in accord with much other experience which shows that there is a special stability to the inert gas electron population. 

Although the electron affinity of fluorine is less than that of chlorine, F2 is more reactive than Cl2. Explain some of the reasons for this difference in reactivity. 

The nearest anionic analogue of H"1 is the F ion. Some of the calculations for it are at first surprising, but parallel those of the proton and are acceptable under closer scrutiny (a) F- forms a stronger covalent bond than Cl" (>Br" > I-) 38 (b) F" is a very strong base with a large transfer of electron density to the acid. This is a result of the low charge capacity (low electron affinity) of fluorine. 

The enthalpy of formation of sodium fluoride is —571 kj mol. Estimate the electron affinity of fluorine Compare your value with that giver in Table 23. 

Unfortunately, few experimental ionization potentials or electron affinities of fluorinated radicals have been reported, and the calculation of such molecular properties is fraught with difficulties, although reasonable trends can be predicted [48-49]. Table 3 provides what numbers are presently available [50-55],... 

Figure 12 reports electron impact cross sections for CF4 [47] and SF6 [48], In the SF6 data it should be noticed the very important attachment cross section for the formation of SF6 and SF5 with low energy electrons [49] which results from the comparable electron affinity of fluorine (3.40 eV) with respect to the dissociation energy of SF6 (bond strength F—SF5 = 3.95 eV), whereas the bond strength F—CF3 is 5.56 eV. 

The energy change for this process corresponds to the electron affinity of fluorine, which is -328 kj/mol. 

Using Fig- 4.7 generate the first five terms of the senes for the Madelung constant for NnCL How close is the summation of these terms to the limiting value given in Table 4.1 The enthalpy of formation of sodium fluoride is —571 kj mol. Estimate Ihe electron affinity of fluorine Compare your value with that ven in Table 23. 

NaK the bond may be regarded as covalent, but in molecules formed from atoms of widely differing electronegativity, e.g, LiCl, NaCl, NaBr, KI, the bond is almost entirely ionic. Caesium fluoride presents a special case however, since the electron affinity of fluorine (95 kcals) is greater than the ionization potential of caesium (89 kcals) so that in the change of caesium and fluorine atoms into ions, a small liberation of energy, amounting to 6 kcals, occurs. 

The symbol IP refers to the ionization potential of the least bound electrons on the indicated species. From the electron affinity of fluorine (3.4 eV) and the first ionization potential for neon (21.6 eV), we have k = 18.2 eV, in agreement with the Hartree-Fock values. 

Based on general trends, the electron affinity of fluorine would be expected to be greater than that of chlorine however, the value is less and is similar to the value for bromine. Explain. 

Electron affinity of fluorine First ionization potential of calcium Second ionization potential of calcium Lattice energy of fluorite Heat of sublimation of calcium Bond energy of fluorine... 

The sign of the enthalpy change indicates that this is an exothermic process however, the electron affinity of fluorine is assigned a value of +328 kJ/mol. Thus we can think of electron affinity as the energy that must be supplied to remove an electron from a negative ion. For the removal of an electron from a fluoride ion, we have... 

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