Explain how two atoms of oxygen can be different

Two atoms of an oxygen atom can be different if they are oxygen isotopes. E. g. ¹⁶O, ¹⁷O,¹⁸O.

Explanation:

¹⁶O, ¹⁷O,¹⁸O are the stable isotopes of the Oxygen atom. While all are functionally Oxygen atom, they have different chemical properties. Isotopes are element containing an equal number of protons and a different number of neutrons.

Along with these stable isotopes, a large number of radioactive isotopes are also formed. However, these are unstable and have relatively short life ranging from minutes to just a few seconds. Evaporation, as well as condensation, are amongst two major process that more or less influence heavy and light oxygen atoms ratio in the atmosphere.