Electron affinities definition

For the atomic level, the experimental values based on the ionization potential and electron affinity definitions for electronegativity and chemical hardness were considered, see Eqs. (3.346) and (3.362), respectively. Nevertheless, the AIM level was formed by appropriate averaging of atoms-in-molecule summation for each of the considered reactivity indices, see Eqs. (4.15b), (3.252) and (3.248), and along of their MOL counterparts of Eqs. (4.15c), (3.346), and (3.362) the polarizability-, electronegativity- and chemical hardness- based aromaticity definitions were formulated with the associate qualitative trends established by Eqs. (4.15a), (4.16), and (4.17), respectively. Yet, for MOL level of computations all major quantum chemical methods for orbital spectra computation were considered, and implemented in the current application for some basics. Because of the quantum observable character of polarizability the related aromaticity scale was considered as benchmark for actual study and it offered the possibility in formulating... 

In this equation, the electronegativity of an atom is related to its ionization potential, 1, and its electron affinity, E. Mulhken already pointed out that in this definition the ionization potential, and the electron affinity, E, of valence states have to be used. This idea was further elaborated by Hinze et al. [30, 31], who introduced the concept of orbital electronegativity. 

Besides the already mentioned Fukui function, there are a couple of other commonly used concepts which can be connected with Density Functional Theory (Chapter 6). The electronic chemical potential p is given as the first derivative of the energy with respect to the number of electrons, which in a finite difference version is given as half the sum of the ionization potential and the electron affinity. Except for a difference in sign, this is exactly the Mulliken definition of electronegativity. ... 

For a given molecule and a given intemuclear separation a would have a definite value, such as to make the energy level for P+ lie as low as possible. If a happens to be nearly 1 for the equilibrium state of the molecule, it would be convenient to say that the bond is an electron-pair bond if a is nearly zero, it could be called an ionic bond. This definition is somewhat unsatisfactory in that it does not depend on easily observable quantities. For example, a compound which is ionic by the above definition might dissociate adiabatically into neutral atoms, the value of a changing from nearly zero to unity as the nuclei separate, and it would do this in case the electron affinity of X were less than the ionization potential of M. HF is an example of such a compound. There is evidence, given bdow, that the normal molecule approximates an ionic compound yet it would dissociate adiabatically into neutral F and H.13... 

Here q represents the coulomb energy of an electron occupying a definite p]h orbital in unsubstituted benzene its value has been estimated to be about —2.7 v. e. = —60 kcal./mole.5 /3 is a resonance integral between adjacent orbitals its value has been estimated to be about —0.85 v. e. = — 20 kcal./mole.6 Sk is a constant, the purpose of which is to allow for the different electron affinities of the different atoms. For Sk > 0, the... 

One more step provides an operational definition. The HOMO level lies, I = ionization energy, below the vacuum level, while the LUMO level lies, A = electron affinity, below it. Thus, the chemical hardness lies midway in the gap and usually is given in units of eV. 

We must be careful with the definition above in many older textbooks, the electron affinity is defined as the energy released when an electron attaches to a neutral atom. This different definition causes (ea) to change its sign. 

The ionization potential and electron affinity of the molecule are I and A, respectively. By constmction, these definitions involve three Hamiltonians (IV-1, N, N+ 1). However, one may define Fukui functions without invoking any actual derivative relative to the number of electrons by using the derivative of the chemical potential relative to the potential [8]... 

D—The definition of electron affinity is the energy change when a ground-state gaseous atom adds an electron. 

This definition may appear somewhat counterintuitive, because the word affinity suggests that we shouldbe referring to the reverse process. That is why Eea is often given as the negative of the enthalpy of reaction 4.8 at T = 0 [62], The definitions are, of course, equivalent and ensure that in most cases, electron affinities will have positive values. 

The potential energy curves of the species AB, AB+, and AB- are used in figure 4.1 to summarize the definitions of the adiabatic ionization energy and electron affinity of AB. Note that the arrows start and end at vibrational ground states (vibrational quantum number v = 0). 

For reproducing as closely as possible diabatic conditions, we have fixed the Cl—Cl bondlength at its neutral equilibrium value. This way, the system depends on two parameters as shown in Figure 1. Previous experimental and theoretical studies on similar systems, [1,18] have shown that electron jump from Li to the acceptor molecule CI2, which has, once relaxed, a positive vertical electron affinity (see Table 1), is likely to take place at a distance d, (see the definition of this parameter in Figure 1) which is superior to the LiCl equilibrium distance (MP2 value 2.0425 A). The description of this phenomenon in terms of MO and states will be briefly recalled in the next section. 

In the next section we shall recall the definitions of the chemical concepts relevant to this paper in the framework of DFT. In Section 3 we briefly review Strutinsky s averaging procedure and its formulation in the extended Kohn-Sham (EKS) scheme. The following section is devoted to the presentation and discussion of our results for the residual, shell-structure part of the ionization potential, electron affinity, electronegativity, and chemical hardness for the series of atoms from B to Ca. The last section will present some conclusions. 

Take care to note the definition of electron affinity given in the text. 

It would be very interesting to speculate on the behavior of the iso-electronic species NH and O atoms. From limited kinetic studies these appear to undergo addition to double bonds as well as abstraction type of reactions.21 22 However no definitive studies have been made on the existence of the insertion type of reaction which would be very much expected for both species, particularly for the O atom, in view of its fairly large electron affinity.8... 

The relationship between the Mulliken definition and that of Jaffe can be shown quite amply. Taking Eq. 5.62 and substituting q +1, we know that the energy, E, of the system will be that of the +1 cation, or the first ionization energy. Likewise for <7=1. the energy will be the negative29 of the electron affinity, so ... 

Note that the definition of electron affinity does not follow the usual thermodynamic convention in ihat a positive electron affinity is exothermic. See Chapter 2. 

It is possible to be more definite about the influence of face on the work function, which is a measure of the electron affinity of the metal. The work function has been shown to depend on crystal face (19). The question of the relationship of the work function and the specific surface energy of the surface to its chemical activity has been discussed by Suhrmann (20). 

Electronegativity is the ability of an atom or molecule to attract electrons. Why then is it (from one definition) the average of the ionization energy and the electron affinity (Eq. 7.32), rather than simply the electron affinity ... 

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