The notion of formal atomic charges in molecules is probably
the most debated issue in quantum chemistry. Although atomic
charge can not be rigorously defined in a unique way, conclusive
evidence is given here which shows that it provides semiquantitative
information about a number of molecular properties in a
very simple and transparent way. In particular, the calculations
of ESCA chemical shifts, diamagnetic shielding of nuclei and
diamagnetic part of the molecular magnetic susceptibility are well
described and thoroughly discussed. Finally, a relation between
the effective atomic charges and total molecular SCF energies is
illustrated by numerical examples. The point-charge description
of the mentioned molecular properties is particularly useful if it
is employed within the framework of semiempirical theories .because
the computational costs are then negligible. The most successful
semiempirical scheme in this respect seems to be the SCC-
MO (self-consistent charge MO) method
