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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.
In any case, the value of the electron affinity of a solid substance is very different from the chemistry and atomic physics electron affinity value for an atom of the same substance in gas phase. For example, a silicon crystal surface has electron affinity 4.05 eV, whereas an isolated silicon atom has electron affinity 1.39 eV.
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]
where I is the ionization potential and A the electron affinity. This expression implies that the chemical hardness is proportional to the band gap of a chemical system, when a gap exists. The first derivative of the energy with respect to the number of electrons is equal to the chemical potential, μ, of the system,
The energy released when an electron is added to a neutral gaseous atom to form an anion is known as electron affinity. [14] 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 ...
This spacing is called the electron affinity (note that this has a different meaning than the electron affinity of chemistry); in silicon for example the electron affinity is 4.05 eV. [16] If the electron affinity E EA and the surface's band-referenced Fermi level E F-E C are known, then the work function is given by
The energy required to remove one or more electrons to make a cation is a sum of successive ionization energies; for example, the energy needed to form Mg 2+ is the ionization energy required to remove the first electron from Mg, plus the ionization energy required to remove the second electron from Mg +. Electron affinity is defined as the ...
Data table: electronegativities of the elements Number Symbol Name electronegativity WEL CRC LNG; 1: H: hydrogen: 2.20: same 2: He: helium: no data: same 3: Li ...