According to the aforementioned rules, the linear I4 -system (5 electrons in the chain for 3 bonds) would be built by using 3 electrons in 3 I•I 2c-1e bonds and adding 2 more at the periphery of the molecule as in the standard Lewis formulas writing. This creates the situation of 2 weakly bound I2 molecules by a single I•I 2c-1e bond. It is also to be noted that in even membered linear In chains there are n/2 bonding MOs and n/2 antibonding MOs, so that I4 -, unlike I3 -or I5 -(see below), starts populating an antibonding level (an unfavourable situation from the energetic point of view). Moreover, the ERMB cannot be formed over more than 3 centers and bending (occurring in the I5 -system explained below) cannot improve global bond order along the chain in the I4 -anion. Moreover, we have to stress that the 2c-1e bond is a kind of multicenter bond (the minimum set for the EDMB is the 3c-2e bond), so there is a lack of a second 2c-1e bond in the I4 -anion, which further supports the lack of experimental evidence of this unit. Lastly, as for other odd-electron species, radicals are in general high-energy species, of overall rare occurrence with respect to even-electron species. As a matter of fact, the I4 -anion has not been experimentally observed to our knowledge. Let us now discuss the linear I5 -case (6 electrons in the chain for 4 bonds). This example allows us to highlight the reason for polyiodides bending and to focus on bond distance alternation. The classical picture for the anion is found in Figure 2c-1e bonds. This configuration allows to populate completely 3 of the 5 MO levels; i.e. the two bonding orbitals and the non-bonding orbital, so it is not so unfavorable as the I4 -case.