  We first argue that the covalent bond and the various closed-shell
interactions can be thought of as symmetry broken versions of one and the same
interaction, viz., the multi-center bond. We use specially chosen molecular
units to show that the symmetry breaking is controlled by density and
electronegativity variation. We show that the bond order changes with bond
deformation but in a step-like fashion, regions of near constancy separated by
electronic localization transitions. These will often cause displacive
transitions as well so that the bond strength, order, and length are
established self-consistently. We further argue on the inherent relation of the
covalent, closed-shell, and multi-center interactions with ionic and metallic
bonding. All of these interactions can be viewed as distinct sectors on a phase
diagram with density and electronegativity variation as control variables; the
ionic and covalent/secondary sectors are associated with on-site and bond-order
charge density wave respectively, the metallic sectorwith an electronic fluid.
While displaying a contiguity at low densities, the metallic and ionic
interactions represent distinct phases separated by discontinuous transitions
at sufficiently high densities. Multi-center interactions emerge as a hybrid of
the metallic and ionic bond that results from spatial coexistence of
delocalized and localized electrons. In the present description, the issue of
the stability of a compound is that of mutual miscibility of electronic fluids
with distinct degrees of electron localization, supra-atomic ordering in
complex inorganic compounds comes about naturally. The notions of electronic
localization advanced hereby suggest a high throughput, automated procedure for
screening candidate compounds and structures with regard to stability, without
the need for computationally costly geometric optimization.
