Are Atoms the Bricks of Molecules?

The celebrations of the International Year of the Periodic Table (IYPT2019) brought to public attention that the 118 atoms, included and systematized in the periodic table, are the building blocks of everything that exists in the universe. We can even go further in that line of thought, by including time, saying that everything that existed in the past, present or the future in the universe is made of atoms: The periodic table is a Window to Eternity. Quantum Mechanics changed the paradigm of looking at atomic and molecular structures by creating the concept of probabilistic charge distributions commonly known as the electronic cloud. But this electronic cloud cannot be reproduced from the superposition of atomic charge distributions except at nuclei and core electron levels. The valence electrons have their distributions strongly affected by constructive and destructive interference to a point where there will be no resemblance to their atomic counterparts. Can we recover the concept of atom from that distorted mess? How do we split the charge density of a bond between the two intervening atoms? What are lone pairs? Do they belong to an atom? What’s a ring (like in benzene)? We will try to bridge the gap between the quantum formulation and the traditional chemical view.