The group oxidation state of +6 is known for all the members apart from oxygen which lacks available d-orbitals for expansion and is limited to a maximum +2 state, exhibited in the fluoride OF 2.
The group oxidation state of +6 is known for all the chalcogens apart from oxygen which lacks available d-orbitals for expansion of its octet and is itself one of the strongest oxidizing agents among the chemical elements. Oxygen is thus limited to a maximum +2 state, exhibited in the fluoride OF 2.