page_title: Electronegativity
section_title: Correlation of electronegativity with other properties
hierarchical_section_title: Electronegativity / Correlation of electronegativity with other properties
caption_attribution_description: Isomer shifts (119Sn w:Mössbauer spectroscopy) for [SnX6]2− ions (X = halogen), plotted againt the sum of the Pauling electronegativities of the halide ligands. Data from Clasen, C. A.; Good, M. L. (1970). Inorg. Chem. 9:817.
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: The wide variety of methods of calculation of electronegativities, which all give results that correlate well with one another, is one indication of the number of chemical properties which might be affected by electronegativity. The most obvious application of electronegativities is in the discussion of bond polarity, for which the concept was introduced by Pauling. In general, the greater the difference in electronegativity between two atoms the more polar the bond that will be formed between them, with the atom having the higher electronegativity being at the negative end of the dipole. Pauling proposed an equation to relate "ionic character" of a bond to the difference in electronegativity of the two atoms, although this has fallen somewhat into disuse.
  Several correlations have been shown between infrared stretching frequencies of certain bonds and the electronegativities of the atoms involved: however, this is not surprising as such stretching frequencies depend in part on bond strength, which enters into the calculation of Pauling electronegativities. More convincing are the correlations between electronegativity and chemical shifts in NMR spectroscopy or isomer shifts in Mössbauer spectroscopy (see figure). Both these measurements depend on the s-electron density at the nucleus, and so are a good indication that the different measures of electronegativity really are describing "the ability of an atom in a molecule to attract electrons to itself".
caption: The variation of the isomer shift (y-axis, in mm/s) of [SnX6]2− anions, as measured by 119Sn Mössbauer spectroscopy, against the sum of the Pauling electronegativities of the halide substituents (x-axis).
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