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The electron affinity of molecules is a complicated function of their electronic structure. For instance the electron affinity for benzene is negative, as is that of naphthalene, while those of anthracene, phenanthrene and pyrene are positive. In silico experiments show that the electron affinity of hexacyanobenzene surpasses that of fullerene. [5]
Electron affinity can be defined in two equivalent ways. First, as the energy that is released by adding an electron to an isolated gaseous atom. The second (reverse) definition is that electron affinity is the energy required to remove an electron from a singly charged gaseous negative ion.
The downward arrow "electron affinity" shows the negative quantity –EA F, since EA F is usually defined as positive. The enthalpy of formation of lithium fluoride (LiF) from its elements in their standard states (Li(s) and F 2 (g)) is modeled in five steps in the diagram: Atomization enthalpy of lithium; Ionization enthalpy of lithium
The energy released when an electron is added to a neutral gaseous atom to form an anion is known as electron affinity. [15] Trend-wise, as one progresses from left to right across a period , the electron affinity will increase as the nuclear charge increases and the atomic size decreases resulting in a more potent force of attraction of the ...
In chemical physics and physical chemistry, chemical affinity is the electronic property by which dissimilar chemical species are capable of forming chemical compounds. [1] Chemical affinity can also refer to the tendency of an atom or compound to combine by chemical reaction with atoms or compounds of unlike composition.
By inserting the energetic definitions of the ionization potential and electron affinity into the Mulliken electronegativity, it is seen that the Mulliken chemical potential is a finite difference approximation of the electronic energy with respect to the number of electrons, i.e.,
Ionization energies calculated from DFT orbital energies are usually poorer than those of Koopmans' theorem, with errors much larger than two electron volts possible depending on the exchange-correlation approximation employed. [3] [4] The LUMO energy shows little correlation with the electron affinity with typical approximations. [9]
Be wary of the sign of electron affinity: traditionally, it was the energy released on formation of the anion (ie positive number = easily formed anion). The sign convention used in this article is consistent with modern enthalp change conventions for formation of the anion, and hence is the other way round (negative number = easily formed anion).