  We analyze two-particle binding factors for the case of \ch{H2} molecule with
the help of our original Exact Diagonalization \textit{Ab Intio} (EDABI)
approach. Explicitly, we redefine the many-particle covalency and ionicity
factors as a function of interatomic distance. Insufficiency of those basic
characteristics is stressed and the concept of \textit{atomicity} is introduced
and corresponds to the Mott and Hubbard criteria concerning the localization in
many-particle systems. This additional characteristic introduces atomic
ingredient into the essentially molecular states and thus eliminates a spurious
behavior of the standard covalency factor with the increasing interatomic
distance, as well as provides a physical reinterpretation of the chemical
bond's nature.

Atomic and Molecular Clusters;Chemical Physics