  Molecular-crystalline duality of graphene ensures a tight alliance of its
physical and chemical natures, each of which is unique in its own way. The
paper examines the physical-chemical harmony and/or confrontation in terms of
the molecular theory of graphene. Chemistry that is consistent with graphene
physics expectations involves: small mass of carbon atoms, which provides a
lightweight material; sp2 configuration of the atoms valence electrons,
ensuring a flat 2D structure of condensed benzenoid units; high strength of C-C
valence bonds responsible for exclusive mechanical strength. Chemistry that is
in conflict with graphene physics expectations covers: radical character of
graphene material; collective character of electronic system of graphene,
preventing from localization of its response on any external impact; the
molecular nature and topochemical character of graphene mechanics; the
molecular nature of graphene magnetism. Each of the properties is a direct
consequence of the odd electron correlation, on one hand, and ensures a high
instability of graphene material, on the other. Electron correlation inhibition
by deposition of graphene monolayers on substrates is seen as a promising way
to solve the problem.
