This rationalization is simple and preserves the double-bond nature of the group 13 or 14 atom interaction. The multiple bond is not exactly a typical σ+π interaction; rather the two halves of the alkyne analogue are treated as singlet bent monomers and the multiple bond is treated as an aggregation between them, with the sp x p y -hybridized filled orbital on one group 13 or 14 atom donating to the vacant p z of the other.