Electronegativity (Mulliken-Jaffe): periodicity

R.S. Mulliken proposed an electronegativity scale in which the Mulliken electronegativity, ΧM is related to the electron affinity EAv (a measure of the tendency of an atom to form a negative species) and the ionization potential IEv (a measure of the tendency of an atom to form a positive species) by the equation:

ΧM = (IEv + EAv)/2

The subscript v denotes a specific valence state - so for trigonal boron compounds, a values of electronegativity can be defined for sp2 hybrid orbitals. If the values of IE and EA are in units of MJ mol-1, then the Mulliken electronegativity ΧM can be expressed on the Pauling scale by the relationship:

ΧM = 3.48[(IEv + EAv)/2 - 0.602]


Pauling scale


Values presented here are largely from reference 1. Mulliken's proposals are to be found in references 2 and 3. Tables of values are also given in references 4 and 5 as well.

Mulliken-Jaffe electronegativities are tabulated for a number of orbitals as well as a consolidated set of values for various orbitals suitable to correlate with Pauling values:

Literature sources

  1. S.G. Bratsch, J. Chem. Ed., 1988, 65, 34.
  2. R.S. Mulliken, J. Chem. Phys., 1934, 2, 782.
  3. R.S. Mulliken, J. Chem. Phys., 1935, 3, 573.
  4. J.E. Huheey, E.A. Keiter, and R.L. Keiter in Inorganic Chemistry : Principles of Structure and Reactivity, 4th edition, HarperCollins, New York, USA, 1993.
  5. A.M. James and M.P. Lord in Macmillan's Chemical and Physical Data, Macmillan, London, UK, 1992.

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