One plausible explanation for this effect is the variation in the hybridization adopted by the dopants. It's possible that the relatively small covalent radii of atoms in second period enable an in-plane X-Mo bonding configuration, benefiting elements with electronic configurations suitable for an sp 2 orbital hybridization. However, as covalent radii increase, higher-period elements from groups 13 and 14 may not be able to adopt this hybridization due to geometric constraints imposed by the sheet. These constraints demand a more vertical interaction be- tween the dopant and Mo, which could account for the comparatively lower bonding energies compared to elements in groups 15 and 16. The latter two groups possess electronic configurations less suited for an sp 2 hybridization, potentially explaining the weaker binding observed in period 2 elements. However, for higher periods, the same electronic configuration, will prove much more favorable for the sp 3 hybridization, resulting in the stronger binding. Therefore, it may be relevant to consider the covalent radii of the dopants and their optimized positions within the sheet when examining these interactions.