▎ 摘　　要

We investigate the effect of full hydrogenation and fluorination on the spin-orbit coupling (SOC) in graphene, silicene and germanene. In chair conformation, the fluorination of graphene increases the spin-orbit splitting , while the hydrogenation and fluorination of other structures reduce the at the -point. In case of boat conformation, the hydrogenation and fluorination reduce the symmetry of honeycomb structure, which in turn remove the degeneracy of valence band maximum at the -point. The change in band gaps due to SOC is very small in boat conformation structures as compared to that in the corresponding chair conformation structures.