In a recent work, the number of electrons shared (ES) and the normalized number of electrons transferred (ET) between two centers has been calculated for typical hypervalent molecules with 3c-4e ERMBs, such as ClF3, XeF2, and SF4 and the less than one electron shared between every bridged B-H pair in diborane (B2H6) On the other hand, Wuttig and coworkers have proposed that metavalent bonding might be seen as a kind of electron-deficient 2c-1e bond, but they have not considered the multicenter character of unconventional bonding in PCMs. This multicenter character of half bonds, which was already suggested by Rundle ("half-bonds occur in pairs") more ). Typically, the ES value of ERMBs is smaller than that of non-polar (ET= 0) covalent bonds, but higher than that of polar (ET≠ 0) single covalent bonds of comparable polarity; i.e. similar ET value. On the other hand, the ES value of EDMBs is smaller than that of single covalent bonds of comparable polarity. Unlike the supporters of the metavalent bonding model, Manjón and coworkers have shown that the term metavalent is unnecessary to describe bonds in PCMs since they are electron-deficient, such as the bridged B-H-B bonds in B2H6 and the bonds in sc-As (or sc-Sb) . Manjón and coworkers consider that metallic bonding is indeed characterized by delocalized electrons and can be qualified as an electron-deficient bond since it is the last step in the process of electron delocalization. However, it should be emphasized that the metallic bond cannot be considered as a multicenter bond because it is not a directional bond, unlike ionocovalent bonds, ERMBs, and EDMBs. In these last three bond types, the total or partial electron localization accounts for the directionality of the bonds.