The role of Pauling and other EN scales in the development of chemistry is undoubted. However, if the EN is the electron attracting ability of atoms (for example H atom), can this H atom attract its electron (or the bonding pair) with the same force toward Na or Cl in NaH or HCl? Will this be the same EN for Na and Cl in NaCl as it was in the NaH and HCl? Would this be the same force in gaseous NaCl and solid NaCl, when the partial charges of atoms (ions) are not the same, the distance between the point like charges are not the same, or if the neighboring point charges number are not the same in modifications with different coordination number?
We feel that a simple approximation method should be entered to calculate new EN values for elements in their different compounds, which could take into consideration these things (and other chemical viewpoints), and which is simpler than quantum chemistry and could be used easily to explain the nature of compounds. I am waiting for opinions about this idea.
Indeed electronegativity is an intuitive concept which cannot be pushed too quantitative. It is useful as a guideline to understand major trends in bonding, but certainly not in predicting detailed properties.
Now this debate is a 80-year old one. Several other electronegativity scales (Allred-Rochow, Sanderson, Allen, Mulliken ....) have been proposed. For instance Mulliken defines electronegativity as the mean between ionization energy (IE) and electron affinity (EA), which allows one to relate electronegativity to the energies of HOMO and LUMO orbitals. Another concept which could be useful in this perspective is the hardness/sofness concept with the eta parameter defined as half the energy difference between IE and AE...
But maybe in your case, Allred-Rochow definition will be more suitable since it is related to to the charge experienced by a valence electron on the surface of an atom/ion.
My impression is that EN is an intuitive, semi-quantitative notion, which is very useful in understanding some chemical phenomena. As, however, is not related to the eigenvalue of any quantum mechanical operator, I see no reason to calculate it more exactly. Obviously Cr(III) is a metal and Cr(VI) behaves as a non-metal, so the EN value should be very different. I see more meaningful to calculate more exact quantum chemical values as atomic charge, bond order etc. and to investigate these porperties in various molecular environments.
The suggested target could be available without using QCC methods, only a simple approximative calculation is planned to determine EN values with more chemical meaning.
It sounds interesting but I think you have to be careful not to go in circles, i.e, if you want to use the new electronegativities to explain the nature of compounds then comprehensive existing information on the nature of compounds cannot be used as an input because the result will be tautologous.
The EN changes primarily with the oxidation state, and perhaps slightly by isotope. It is inherently related to the electronic properties of the nuclei involved and is generally viewed as a relative semi-empirical constant.
You could develop semi-empirical equations utilising electronegativity for the estimation of chemical properties, however it would have to be capable of demonstrating some predictive power to be of value.
Dear Eric,
thank you for answer. One of our target with development of this new EN value is prediction of properties of the radioactive elements and theirs compounds to estimate their chemical properties.
Indeed electronegativity is an intuitive concept which cannot be pushed too quantitative. It is useful as a guideline to understand major trends in bonding, but certainly not in predicting detailed properties.
Now this debate is a 80-year old one. Several other electronegativity scales (Allred-Rochow, Sanderson, Allen, Mulliken ....) have been proposed. For instance Mulliken defines electronegativity as the mean between ionization energy (IE) and electron affinity (EA), which allows one to relate electronegativity to the energies of HOMO and LUMO orbitals. Another concept which could be useful in this perspective is the hardness/sofness concept with the eta parameter defined as half the energy difference between IE and AE...
But maybe in your case, Allred-Rochow definition will be more suitable since it is related to to the charge experienced by a valence electron on the surface of an atom/ion.
P.S. Forgot to mention this article on the bonding in ionic crystals:
http://pubs.acs.org/doi/pdfplus/10.1021/jp106370z
According to contemporary views, electronegativity of an element depends upon its valence state. Moreover, not only electronegativity of atoms is discussed now, but also the above value for atomic groups, radicals, and molecules. Absolute definitions of electronegativity, along with hardness and softness, are among the bases of comprehensive theory of substances' reactivity. Well-known are old works by R.G. Parr, R.G. Pearson, R.J. Boyd, J. Mullay, N. Inamoto and Sh. Masuda, S.G. Bratsch, L.C. Allen, S. Hati and D. Datta, et al.
You can compute atomic electronegativities using Chemosophia Elastic model (see www.chemosophia.com "Single molecule calculations (molecular and atomic characteristics, multiconformational analysis, superimposition of conformers, electron properties)" or "Large organic and elementorganic molecular systems (up to 10 000 atoms in a molecule)" services) now for free. Really, the EN is various in different compounds for the same element.
I respect the answers of all friends. In fact EN of an element depends on the nature and number of atoms attached to a particular atom. It also depends on the state of hybridization of an element. For example the EN of P in PF3 is high than its EN in PCl3. Here it depends on the nature of bonding atoms. Similarly, EN of P in PF5 is high than its EN in PF3. Here it depends on the number of bonding atoms. EN of C is high in sp state than sp2 which is high than sp3. Thus EN of the same element is different in different compounds. Here it depends on the mode of hybridization.
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