text: oxygen is an element, O would be one atom of this element\n\nO does not really exist for very long in nature, because it has only 6 electrons.  it reacts with almost anything that it comes in contact with.\n\nO2 is simply two oxygen atoms double bonded together to complete their outer shells.  the atmosphere we breath is 20% O2.  there is no O in the atmosphere, or anywhere else for that matter.\n\nyou can find out all about it and see pictures here\nhttp://en.wikipedia.org/wiki/Oxygen