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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 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]
The Mulliken electronegativity can only be calculated for an element whose electron affinity is known. Measured values are available for 72 elements, while approximate values have been estimated or calculated for the remaining elements. The Mulliken electronegativity of an atom is sometimes said to be the negative of the chemical potential. [14]
Noble gases cannot accept an electron to form stable anions; that is, they have a negative electron affinity. [32] The macroscopic physical properties of the noble gases are dominated by the weak van der Waals forces between the atoms.
Chemically, the nonmetals mostly have higher ionisation energies, higher electron affinities (nitrogen and the noble gases have negative electron affinities) and higher electronegativity values [n 1] than metals noting that, in general, the higher an element's ionisation energy, electron affinity, and electronegativity, the more nonmetallic ...
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 ...
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)). The total ground state energy thus becomes −14.359 888 eV.
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]