page_title: Electronegativity
section_title: Mulliken electronegativity
hierarchical_section_title: Electronegativity / Methods of calculation / Mulliken electronegativity
caption_attribution_description: The correlation between Pauling electronegativity (y-axis, revised values) and Mulliken electronegativity (x-axis, in kJ/mol)
context_page_description: Electronegativity, symbol χ, measures the tendency of an atom to attract a shared pair of electrons. An atom's electronegativity is affected by both its atomic number and the distance at which its valence electrons reside from the charged nucleus. The higher the associated electronegativity, the more an atom or a substituent group attracts electrons.
  On the most basic level, electronegativity is determined by factors like the nuclear charge and the number and location of other electrons in the atomic shells.
  The opposite of electronegativity is electropositivity: a measure of an element's ability to donate electrons.
  The term "electronegativity" was introduced by Jöns Jacob Berzelius in 1811,
  though the concept was known before that and was studied by many chemists including Avogadro.
  In spite of its long history, an accurate scale of electronegativity was not developed until 1932, when Linus Pauling proposed an electronegativity scale which depends on bond energies, as a development of valence bond theory. It has been shown to correlate with a number of other chemical properties.
context_section_description: Robert S. Mulliken proposed that the arithmetic mean of the first ionization energy (Eᵢ) and the electron affinity (Eₑₐ) should be a measure of the tendency of an atom to attract electrons. As this definition is not dependent on an arbitrary relative scale, it has also been termed absolute electronegativity, with the units of kilojoules per mole or electronvolts.
  However, it is more usual to use a linear transformation to transform these absolute values into values that resemble the more familiar Pauling values. For ionization energies and electron affinities in electronvolts,
  and for energies in kilojoules per mole,
  The Mulliken electronegativity can only be calculated for an element for which the electron affinity is known, fifty-seven elements as of 2006.
  The Mulliken electronegativity of an atom is sometimes said to be the negative of the chemical potential.  By inserting the energetic definitions of the ionization potential and electron affinity into the Mulliken electronegativity, it is possible to show that the Mulliken chemical potential is a finite difference approximation of the electronic energy with respect to the number of electrons., i.e.,
caption: The correlation between Mulliken electronegativities (x-axis, in kJ/mol) and Pauling electronegativities (y-axis).
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