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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 broad definition, used generally throughout history, is that chemical affinity is that whereby substances enter into or resist decomposition. [ 2 ] The modern term chemical affinity is a somewhat modified variation of its eighteenth-century precursor "elective affinity" or elective attractions, a term that was used by the 18th century ...
Similarly, nucleophilicity is defined as the affinity of an electron-rich species, known as a nucleophile, to donate electrons to another species. [29] Trends in the periodic table are useful for predicting an element's nucleophilicity and electrophilicity.
The ion has two electrons bound by the electromagnetic force to a nucleus containing one proton. The binding energy of H − equals the binding energy of an extra electron to a hydrogen atom, called electron affinity of hydrogen. It is measured to be 0.754 195 (19) eV or 0.027 7161 (62) hartree (see Electron affinity (data page)).
While Koopmans' theorem was originally stated for calculating ionization energies from restricted (closed-shell) Hartree–Fock wavefunctions, the term has since taken on a more generalized meaning as a way of using orbital energies to calculate energy changes due to changes in the number of electrons in a system.
The electron affinity (usually given by the symbol in solid state physics) gives the energy difference between the lower edge of the conduction band and the vacuum level of the semiconductor. The band gap (usually given the symbol E g {\displaystyle E_{\rm {g}}} ) gives the energy difference between the lower edge of the conduction band and the ...
The higher the proton affinity, the stronger the base and the weaker the conjugate acid in the gas phase.The (reportedly) strongest known base is the ortho-diethynylbenzene dianion (E pa = 1843 kJ/mol), [3] followed by the methanide anion (E pa = 1743 kJ/mol) and the hydride ion (E pa = 1675 kJ/mol), [4] making methane the weakest proton acid [5] in the gas phase, followed by dihydrogen.