The contrasting geometrical features between organic and inorganic counterparts of amines and oxanes are explained in terms of an offset between attractive (donor- acceptor) and repulsive (donor-donor) interactions. Natural bond orbital (NBO) calculations carried out at the density functional theory level of theory reveal that hyperconjugative effects in the organic amines and ethers are overcome by repulsive interactions occurring between the lone pair on the nitrogen/oxygen atom and the adjacent sigma(C-R) bond orbitals. Although displaying lower energies than in the corresponding organic derivatives, the LP(X) -> sigma*(E-R) (X = N, O; E = Si, Ge, Sn) interactions in heavier counterparts overcome the LP(X)center dot center dot center dot sigma(E-R) repulsions, impacting thus their structural behavior. In addition, NBO deletion optimizations emphasize that among hyperconjugations, back-bonding effects of the LP(X) -> d(E) type dictate to a lesser extent the anomalous structures of the inorganic amines and oxanes.