Atoms in Molecules Theory has been applied to analyze bonding properties, in potentially hypervalent pnicogen (N, P or As)-chalcogen(O or S) bonds within the framework of three plausible models: (i) one s bond and two p back-bonds (negative hyperconjugation), (ii) one s bond and three s back-bonds, and (iii) three W (banana) bonds. The topological analyses (based upon the electron charge density ( r(r), its Laplacian, Ѳr(r), bond ellipticity, etc.) and the charges were consistent with a highly polarized sigma bond, with bond strength dependent on the electrostatic interactions. The equilibrium geometries were optimized by both density functional theory with a hybrid functional (B3LYP) and by ab initio methods at the MP2(full) level, using the 6-311G basis set augmented by polarization and/or diffuse functions.