Final answer:
OF₄ is expected to be non-existent because oxygen does not typically form stable compounds with four fluorine atoms due to its common -2 oxidation state, and its chemistry does not support such a compound.
Step-by-step explanation:
Among the molecules listed, the one that would be expected to be non-existent is OF₄. The other molecules, OF₂, SF₂, SF₄, and SF₆, are known to exist based on the common oxidation states of oxygen and sulfur. Oxygen typically forms compounds in the -2 oxidation state, and the existence of dioxygen difluoride (OF₂) is consistent with this. Conversely, OF₄ suggests an oxidation state for oxygen that is not chemically feasible with these elements as oxygen's most common positive oxidation state is +2 in compounds like oxygen difluoride (OF₂), where it is already bonding with two atoms of fluorine. Sulfur, which has a d-orbital, can expand its octet to form SF₂, SF₄, and SF₆, with each respectively having two, four, and six fluorine atoms.