In this section, we will dive into the effect of changing the Group 14 central atom of a metallylene: from carbenes to silylenes to germylenes to stannylenes to plumbylenes. When going down Group 14, the electronegativity of the element decreases. Besides that, the atomic radius and nuclear charge increase, thereby increasing the energy difference between ns and np orbitals (vide infra), which leads to a 'lower tendency to hybridize' for the larger elements. 30 This explains the singlet electronic configuration of the heavier metallylenes, bearing a vacant p-type orbital perpendicular to the occupied lone pair orbital, Scheme 2a. Recently, our group studied small molecule activation, like H2, CO2, H2O, NH3, PH3, CH4, BF3, and HCN, by using simple model singlet metallylenes H 3 C-E-L, where E is a Group 14 element and L is a nitrogen or phosphorus ligand, with density functional theory (DFT). The energy barrier increases when the central atom changes from C to Si to Ge to Sn, and the reaction energy becomes less stable along the same order, Figure . The trend in energy barrier was analyzed by using the activation strain model (ASM) 32 and a canonical energy decomposition analysis (EDA) 33 within Kohn-Sham molecular orbital theory. Before discussing the results from the analyses, we explain the methodologies used. The activation strain model is a fragmentbased method that decomposes the electronic energy into the