Abstract
The review presents the results of a number of studies where various integral characteristics of the effective dimensions of quantum-mechanical systems have been derived and justified by interpreting the square of the modulus of the wave function using probability theory. The concepts of the types of electron delocalisation in atoms and molecules and quantities which can serve at its measure as well as hypotheses concerning the integral characteristics of the charge distribution between the effective volume of an atomic-molecular system and the surrounding space are discussed. The above characteristics have been calculated for a number of specific quantum-mechanical systems, in particular for some of the simplest atoms and molecules.
The bibliography includes 34 references.