Allred-Rochow vs Pauling Electronegativity scale While observing the trends in electronegativity of the elements, I found a discrepancy between Allred-Rochow and Pauling scales. In Pauling's scale, chlorine is the third most electronegative element ($\ce{F &gt; O &gt; Cl &gt; N}$). In Allred-Rochow's, it is the fourth ($\ce{F &gt; O &gt; N &gt; Cl}$).

While of course the numeric values of the two scales are different, I thought that the rank of the elements would be the same, being electronegativity related to the properties of the atoms (for instance, the partial charge of molecules such as nitrogen trichloride relies on the electronegativity).

So, I was wondering: which scale is more accurate? And, if one is wrong, why are both scales still in use?
Pauling's electronegativity scale is determined by considering the strengths of A-A, A-B, B-B bonds.

Allred-Rochow's electronegativity is determined by considering the charge experienced by an electron on the "surface" of the atom.

While the correlation between the two scales is not perfect, it is quite good, since the scales are calculated with different methods:




  The correlation between Allred–Rochow electronegativities (x-axis, in &Aring;−2) and Pauling electronegativities (y-axis).
  By Physchim62 GFDL, CC-BY-SA-3.0, from Wikimedia Commons


Also the partial charge is a model, useful in order to make rapid evaluations on real things. Sometimes, when molecules with almost covalent bonds (such as nitrogen trichloride) are modeled with different electronegativity scales, the partial charge may be different, but the actual electron cloud may not agree with the model.

The real electron density can be then calculated with quantomechanical methods, which are much more accurate and yet complicated than the simple model of electronegativity.