This book is a contribution to the debate on the implications of the information theory of quantum systems for the description of numerous quantum phenomena of the electronic structure. It contains several applications of the basic concepts, techniques, and relations of the information theory to selected problems of atomic and molecular structure and chemical reactivity. Such treatment gives rise to the information-entropic representation of the atomic and molecular states, which complements the familiar energy representaton of the density-functional and wave-function-based theories. The most...