Time Evolution of the Electronegativity - Modern Trends in Chemistry and Chemical Engineering - page 22

pointed out that the two fundamental atomic parameters; hardness and electronegativ-
ity are proportional to each other.
Ghosh and Islam [17-20, 22, 40, 41] opined that electronegativity is not an ob-
servable property and hence, no quantum mechanical operator can be assembled for
its quantum mechanical evaluation. It is an empirical quantity and remains empiri-
cal. So, there is a plenty scope of research on this domain. Allen [13, 14] suggested
that the concept and scale of electronegativity have a “broken symmetry” symmetry
relationship with Periodic Tables categorization, which completes the Periodic Table.
Following Pauling, some scientist believe that electronegativity is an in situ property
developed on molecule formation rather it is an intrinsic ground state property of atom
and it is carried in to molecules but a majority of scientists [13, 14, 22, 25, 48-53],
have established that electronegativity is a free atom property. Allen et al. [105, 106]
opined that the in situ assumption is self defeating and so the electronegativity is very
diffi cult to defi ne.
CONCLUSION
From the above discussions, it is self evident that no rigorous definition of electro-
negativity has been suggested so far and the final scale of electronegativity is yet to
develop. The problem of unit of electronegativity is probably solved in favor of energy
unit. It is also argued that electronegativity is not an in situ but an intrinsic free-atom,
ground-state property.
The concept of electronegativity and electron attracting power of an atom bonded
to divergent atoms are now accepted as true “in each other's pocket.” This electron
attracting power originates from the effective nuclear charge. It, therefore, transpires
that electronegativity is a fundamental property of atomic shell structure and obvi-
ously periodic in nature.
Finally, we may conclude that the electronegativity is a fundamental descriptor of
atoms molecules and ions which can be used in correlating a vast fi eld of chemical
knowledge and experience. During the chemical event of molecule formation, there
is a physical process of electronegativity equalization through the rearrangement of
charge. The attempts to refi ne the concept and scale of electronegativity theory are not
yet suffi ciently complete to enable a judgment to be reached on their effectiveness. We
quote original from Pritchard and Skinner,
Meanwhile, it seems safe to say that the chemist will continue to make use of the
crude electronegativity theory for some time yet-a practice for which he can hardly be
blamed in the absence of an alternative theory of equal generality.
The applications of the concept of electronegativity are an animated fi eld of cur-
rent research. In Part 2 of this work some of the major applications of electronegativity
in the real world of molecular chemistry and molecular biology are reviewed.
ACKNOWLEDGMENT
We wish to express our sincere thanks to Professor D.C. Ghosh, PRS, PhD, University
of Kalyani for his invaluable teaching, discussions and comments on this topic.