Animals breathe in oxygen from the air. We need oxygen to break down the food we eat and to release energy. When oxygen reacts with food, it forms carbon dioxide, which we breathe out. So we breathe out less oxygen and more carbon dioxide, than we breathe in. Iron is an element and all elements contain only one kind of atom.
Iron contains only iron atoms.
Water does contain oxygen. Each molecule of water, chemically known as H 2 O contains 2 hydrogen atoms and an oxygen atom. Ozone molecules are made of 3 oxygen atoms. The chemical formula for ozone is O 3 . Molecules of iron oxide contain iron atoms and oxygen atoms.