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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]
Electronegativity is not a uniquely defined property and may depend on the definition. The suggested values are all taken from WebElements as a consistent set. Many of the highly radioactive elements have values that must be predictions or extrapolations, but are unfortunately not marked as such.
Robert Sanderson Mulliken ForMemRS [1] (June 7, 1896 – October 31, 1986) was an American physical chemist, primarily responsible for the early development of molecular orbital theory, i.e. the elaboration of the molecular orbital method of computing the structure of molecules.
In a modified Mulliken population analysis, [5] this problem can be reduced by dividing the overlap populations between the corresponding orbital populations and in the ratio between the latter. This choice, although still arbitrary, relates the partitioning in some way to the electronegativity difference between the corresponding atoms.
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.
This connection comes from the Mulliken electronegativity scale. 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.,
Mulliken population analysis is based on electron densities in molecules and is a way of dividing the density between atoms to give an estimate of atomic charges. In transmission electron microscopy (TEM) and deep inelastic scattering , as well as other high energy particle experiments, high energy electrons interacts with the electron cloud to ...
Their Table 1 gives calculated absolute (Mulliken) electronegativities of 2.18 eV for Cs and 2.28 eV for Fr (and 2.72 eV for element 119), so the trend is as you have said. However conversion to the Pauling scale using χ P = 0.187 (E i + E ea ) + 0.17 = 0.374 χ M + 0.17 gives χ P = 0.985 for Cs and 1.023 for Fr.