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Linus Pauling created the electronegativity scale by comparing the
dissosiation energies of homonuclear diatomic molecules, i.e. of the form
A-A, B-B, with the heteronuclear diatomic molecules, A-B. He noticed that
the difference of the dissociation energies, Delta = Diss(A-B) -½{Diss(A-A)
+ Diss(B-B)}, was always positive; I denote the dissociation energy by
'Diss'. The difference of the electronegativities of A and B was then
defined as
0.102*sqrt(Delta)
The coefficient 0.102 is 1/sqrt(96), i.e. conversion from electron volts to
kilojoules. By fitting he was able to find out the individual values of
electronegativity which resulted in a rather linear relationship according
to the equation above.
Electronegativity thus is not an absolute quantity, it is a practical tool,
which does reflect the ability of pulling electrons.
--
Lasse Murtomäki
Helsinki University of Technology
Lab. Phys. Chem. Electrochem.
[EMAIL PROTECTED]
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