Which of the following is NOT an ion of oxygen?

Ozone, represented as O3, is not an ion of oxygen but rather a molecule consisting of three oxygen atoms. While it contains oxygen and plays a critical role in atmospheric chemistry, it does not possess a net charge and therefore does not qualify as an ion.

In contrast, the other choices represent ions of oxygen. O2- signifies the oxide ion, which carries a negative charge due to the gain of two electrons. O-, the superoxide ion, also carries a negative charge due to the gain of an additional electron. O2+, on the other hand, would be a cation of oxygen, which is relatively rare, indicating it has lost two electrons.

Thus, the correct answer is that O3 does not represent an ion of oxygen, but a molecular species instead.