A new scale for electronegativity

[Wrichik Basu]

Electronegativity has seen a number of scales throughout its years of existence. Starting from the Pauling scale to the Allen scale, Wikipedia has a long list.

Recently, Martin Rahm, Tao Zeng and Roald Hoffmann have defined a new scale for electronegativity. The news has been published in ScienceDaily, and the main paper has been published in the Journal of American Chemical Society.

As per ScienceDaily, the new definition is the average binding energy of the outermost and weakest bound electrons -- commonly known as the valence electrons. It has a similarity to the Allen Scale, but is different from it. The new scale encompasses 96 elements, a marked increase from previous versions. The scale now runs from the first element, hydrogen, to the ninety-sixth, curium.

We introduce a new electronegativity scale for atoms, based consistently on ground-state energies of valence electrons. The scale is closely related to (yet different from) L. C. Allen’s, which is based on configuration energies. Using a combination of literature experimental values for ground-state energies and ab initio-calculated energies where experimental data are missing, we are able to provide electronegativities for elements 1–96. The values are slightly smaller than Allen’s original scale, but correlate well with Allen’s and others. Outliers in agreement with other scales are oxygen and fluorine, now somewhat less electronegative, but in better agreement with their chemistry with the noble gas elements. Group 11 and 12 electronegativities emerge as high, although Au less so than in other scales. Our scale also gives relatively high electronegativities for Mn, Co, Ni, Zn, Tc, Cd, Hg (affected by choice of valence state), and Gd. The new electronegativities provide hints for new alloy/compound design, and a framework is in place to analyze those energy changes in reactions in which electronegativity changes may not be controlling.

Journal Reference:

Martin Rahm, Tao Zeng, Roald Hoffmann. Electronegativity Seen as the Ground-State Average Valence Electron Binding Energy. Journal of the American Chemical Society, 2018; 141 (1): 342 DOI: 10.1021/jacs.8b10246

I couldn't read the original publication as I don't have a subscription, but I am interested in hearing from someone who can view the full article.

 

[DrDu]

Another EN scale to torture students...

 

[Wrichik Basu]

Another EN scale to torture students...

It will be a long time before it becomes torture. The IUPAC Compendium of Chemical Terminology (Gold Book) says this:

Electronegativity - Concept introduced by L. Pauling as the power of an atom to attract electrons to itself. There are several definitions of this quantity. According to Mulliken it is the average of the ionization energy and electron affinity of an atom, but more frequently a relative scale due to Pauling is used..

As the IUPAC still prefers the Pauling scale, this new scale won't enter the syllabus very soon. Researchers might use it, but that is a different issue.

 

[Ygggdrasil]

For reference, here is the new scale:

(Figure 3 from https://pubs.acs.org/doi/10.1021/jacs.8b10246)