Hückel rule (4n + 2) for aromatic systems can be written in a different form, in the form of 2n where n - unpaired number. So, we have: 2, 6, 10, 14, 18, etc. This is also true for the electron shells in the atom and aromatic systems. The principle of the interaction of fermions always one, everywhere.
The reason for the formation of the chemical bond is still not clear, in fact, there is no physical justification, as it was at the time of Bohr, since the formation of a chemical bond does not follow from the four fundamental interactions. Just imagine, a chemical bond "does not understand" that it can not be explained normally and quietly exists
:). A full explanation of the chemical bond can only be provided by quantum mechanics (in the future), classical approaches simply do not work.
To understand this, it is necessary not to forget what L. Pauling did (L. Pauling, "The nature of the chemical bond", and the work of L. Pauling: Chem. Rev. 5, 173 (1928)), namely Pauling analyzed the interaction of the hydrogen atom and the proton in the entire range of lengths (he admitted that the hydrogen atom and H + on the approach are preserved and showed that the bond is not formed in this case (since there is no exchange interaction or resonance by Pauling)). Only one of the above-mentioned facts actua