Fully relativistic density-functional calculations have been performed for group 7 oxychlorides MO3Cl, where M=Tc, Re, and element 107, Bh. The results have shown the Bh compound to be thermochemically stable and the most stable towards reduction. Due to increasing dipole moments and electric dipole polarizabilities in the group, volatility of the MO3Cl compounds proved to change as TcO3Cl > ReO3Cl > BhO(3)Cl. For gas-phase chromatography experiments, the adsorption enthalpy of the molecules on the surface of a chromatography column has been predicted as -78 +/- 5 kJ/mol.