A Debate with Pauling on Electronegativity

J. Am. Huilin Ins. 2011, 11, 1-5

 

Journal of

American Huilin Institute

ISSN 2160-438X

http://www.amhuilin.com/journal/jahi

Article

A Debate with Pauling on Electronegativity


Yonghe Zhang


American Huilin Institute, http://www.amhuilin.com

E-Mail: y.zhang.huilin@gmail.com

 

Received:4 October 2011; in revised form:25 October 2011 / Accepted: 29 October 2011

Published: 8 November 2011.


 

The electronegativity was defined in 1932 by Pauling as the power of an atom in a molecule to attract electrons to itself [1]. The concept could be considered as an approximation intuitively appealing for qualitatively understanding the chemical bond by a measure of the tendency of the atom to form ionic compound of an A-B bond will depend on the difference in the electronegativities of the two atoms. However, the Pauling definition has confused the chemistry community for almost a century. The major difficulty is that the attraction for an electron is clearly not expected to be the same for different valencies of an element [2]. And the Pauling electronegativity scales are only one datum per element that based on a limited situation of the linear difference of the thermochemical energy of two elements (H and Cl) unconditionally extended to the all elements. And so that sometime has misled to the opposite wrong results [3-5].

Not an unambiguous definition of the valence state and much less a direct way of the scale led to various methods to construct Pauling electronegativity scales. However, the attempts to derive a comprehensive quantitative scale of electronegativity have been disappointed because the lack of correlation between the experimental quantities and scale over a wide range of the electron quantum configurations.

In 1981, the author [6], based on the Bohr energy model,

E = - Z2me4/8n2h2ɛ02 = - RZ2/n2

obtained the effective principal quantum number n* and the effective quantum nuclear charge Z* from the ionization energy by spectroscopy: 

 

Z*=n*( Iz /R)½

 

Then the first scale of the orbital electronegativity in valence states based on spectroscopy corresponding quantum electron configurations of the orbital from 1s to nf was proposed [6, 7]:

 

Xz = 0.241 n*(Iz /R)½/r2 + 0.775

 

where Iz is the ultimate ionization energy for outer electrons of the s, p, d and f orbital of the atom. R is the Rydberg constant, R = 2p2µ42e4/h2 = 13.6eV, h is Planck’s constant and n*(Iz /R)½ is the effective nuclear charge Z* felt by the valence electron at the covalent boundary r.

Built-up the various quantum parameters of the atomic orbital Iz(s,p,d,f), n*, Z*, rc , rc-1, n*rc-1, based on spectroscopy, the electronegativity Xz formed a Method of the multiple-functional prediction which can explain chemical observations of elements of all orbital electron configurations from 1s to nf, including the σ-bond, the linear or nonlinear combinations of ionic bond and covalent bond, the orbital spatial overlaps and the orbital spatial crosslinks. Therefore, this is what have been expected orbital ionization energy electronegativity that best meets the Cherkasov conclusion [8] and up to Bergmann-Hinze criterion [9].

After the above electronegativity published we received hundred letters and cards. As they said, there might be no more the confusion of electronegativity. But Pauling was still in the confusion and continued to maintain his ambiguous valence state [10]: “I must say that I am not able to form a reliable opinion about the value of your work. I note that for a number of the elements your calculated values are close to my values of the electronegativity, and also that for other elements there is a considerable deviation. I suggest that you might discuss some property of the elements, in various compounds, and in different valence states, in order to find out whether or not your values are helpful in understanding the properties.”

To replay Pauling's concerns, the author published two papers “Electronegativities of elements in valence states and their applications” and “A scale for strengths of Lewis acids” [11], wherein 126 metal ion Lewis acids, in various compounds, and in different valence states, are calculated from:

 

Z = z/r2 - 0.77 Xz + 8.0

 

Where Xz is Zhang electronegativity in valence state and z is the charge number of the atomic core (the number of valence electron). Z is Lewis acid strength. The Z values give a quantitative scale of the relative Pearson hardness or softness for various Lewis acids and agree fairly well with the Pearson classification [12] and the previous work [13-17].

Portier et al. [18] and Lenglet [19] published review on Zhang electronegativity and Lewis acid strengths. The Brown Lewis acid strength Sa [20, 21], Portier ICP [22, 23], Lenglet’s RP Relationship[2425], “Electron-acceptor- Strength” [2627], Scattering Cross Section Q [28-31] and more applications are derived from Zhang electronegativity. We don’t know if Pauling had no more confusion of electronegativity? But we do know somewhere is still in confusion of electronegativity.

Recently, based on the correlation [74-77] between ionocovalency of bond dual nature, the quantum potential term of Schrödinger’s Wave Equation and the spectroscopy data of atom,

 

I(Z*)C(rc-1) = Ze2/r = n*(Iz/R)½rc-1

that describes the dual properties of the bond strength, the charge density and the ionic potential, Zhang proposed an ionocovalenct orbital hybrid scale IC which can be well used as an absolute electronegativity:

IC = n*(Iz/R)½rc-1

And as an application of ionocovalency, a relative electronegativity IC-potential was also obtained:

Xic =0.412 n*(Iz/R)½rc-1 + 0.387

(The electronegativity scale Xz can be accounted for IC-force scale [6,7,75] )

Being composed of the ionocovalent dual nature and the built-up quantum potential parameters of all electron configurations from 1s to nf based on the spectroscopy, the scales can quantitatively describe chemical observations of all elements and have more versatile and exceptional applications than the traditional electronegativity scales and molecular properties.

Over the 30 year, as Zhang electronegativity Xz has been widely quantitatively used [2-9,16-77], it might be unnecessary to use ionocovalency as an electronegativity.

 

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