"Electronegativity is the power of an atom when in a molecule to
attract eletrons to itself." The electronegativity will depend
upon a number of factors including other atoms in the molecule,
the number of atoms coordinated to it, and the oxidation number
for the atom. There are a number of ways to produce a set of
numbers which represent electronegativity scales. The Pauling
scale is perhaps the most famous. He noticed that the bond
energy E(AB) in a molecule AB is always greater than the mean of
the bond energies E(AA) + E(BB) in the homonuclear species AA
and BB. His argument was that in an "ideal" covalent bond E(AB)
should equal this mean, and that the "excess" bond energy is
caused by electrostatic attraction between the partially charged
atoms in the heternuclear species AB. In effect, he was saying
that the excess bond energy arises from an ionic contribution to
the bond. He managed to treat this ionic contribution by the
equation E(AB) = [E(AA).E(BB)]1/2 + 96.48(ΧA - ΧB)2 in which
E(AB) is expressed