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Does the electronegativity only qualitatively describe bond polarity, or does it have any quantitative use? Is it possible to describe electronegativity in terms of other periodic properties, like valence electrons, $Z_{eff}$, etc. (thus eliminating the need of a separately defined value)?

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    $\begingroup$ 1) Actually, it does not have quantitative use. 2) No, or not easily. However, usually it is enough to know that it grows from down to top and from left to right with several additional relatiosn near top-right and top-left corners of the Periodic Table. $\endgroup$ – permeakra Jul 5 '13 at 9:56
  • $\begingroup$ Aside from what permeakra said, electronegativity is not a constant property of an atom/ion. It changes in the different bonding environments and it is only defined for the use of covalent bonds. Mulliken introduced the 'absolute' EN, the mean of ionisation energy and electron affinity, thus formally getting rid of it's necessity. $\endgroup$ – Martin - マーチン Sep 13 '15 at 7:26
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True, with values of electronegativity in hand (and beside the by Pauling, there are others by Rochow, Mulliken, etc. to name some scales) you describe bond polarity. Beyond this number, infrared vibrational frequencies, chemical shifts in NMR spectroscopy and isomer shifts in Mössbauer spectroscopy are mentioned by the corresponding wikipedia article.

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It totally depends at which level you are studying chemistry. If at high school, then practically you dont need the values as such. If, at a higher level then maybe, but still it doesn't have an extensive usage. As far as I have learnt, and at my level we learn Electronegativity only to understand the relative acceptance of electrons by different elements. We have the Mulliken, Pauling and Allred Rochow scale out of which the Pauling scale is famously used. You should know the varying trend of Electronegativity acrros the period and down the group. And as such, Electronegativity doesn't have exceptions as compared to the other periodic properties.

The most important use of Electronegativity is finding out the character if compounds. Where you determine their ionic character. You also realise the Bond strength and Bond length based on the difference of Electronegativity of the two elements(delta EN). You can also understand whether the compound will have polarity/partial polarity or not. And there is a formula to it also where the Ionic character %= 3.5 (delta EN)^2 +16(deltaEN).

This is how much I know about Electronegativity. Hope your doubt has been cleared. :-)

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