If

is the
probability of finding an electron in the volume element

at the point of a molecular entity with coordinates

,
then

is the electron density at this point. For many purposes (e.g. X-ray
scattering, forces on atoms) the system behaves exactly as if the electrons were spread out
into a continuously distributed charge. The term has frequently been wrongly applied
to negative
charge population.
Source:
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1110
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
https://doi.org/10.1351/goldbook.