Describing strongly interacting electrons is one of the crucial challenges of modern quantum physics.

A comprehensive solution to this electron correlation problem would simultaneously exploit both

the pairwise interaction and its spatial decay. By taking a quantum information perspective, we

explain how this structure of realistic Hamiltonians gives rise to two conceptually different no-

tions of correlation and entanglement. The first one describes correlations between orbitals while

the second one refers more to the particle picture. We illustrate those two concepts of orbital

and particle correlation and present measures thereof. Our results for different molecular systems

reveal that the total correlation between molecular orbitals is mainly classical, raising questions

about the general significance of entanglement in chemical bonding. Finally, we also speculate on

a promising relation between orbital and particle correlation and explain why this may replace the

obscure but widely used concept of static and dynamic correlation.

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