where : denotes a LEP, -the covalent bond, and ••• the 3c-4e bond. Stated in words, the halogen bond can be thought as arising from resonance between the LEP of the Y moiety and a covalently bonded fragment (X-R). Notice that the formal equivalence of a 3c-4e bonding view and a n→σ* charge transfer was noted by Chen and Hoffmann. As shown in the opening, 2c-1e EDMB arise instead from the resonance between a bonded and a non-bonded situation, like the one encountered in an infinite linear I∞ chain (Figure ). Therefore, it can be concluded that 3c-4e multicenter bonds are fundamentally different from 2c-1e multicenter bonds (although they share partial bond order and strong directionality). In particular, we have shown that halogen bond formally belongs to the first category (3c-4e) and demonstrated that long bonds in polyiodides formally belong to the second one (2c-1e). Consequently, the two bonding situations are not at all equal.