Oxygen Oxygen and its compounds play a key role in many of the important processes of life and industry. Oxygen in the biosphere is essential in the processes of respiration and metabolism, the means by which animals derive the energy needed to sustain life. Furthermore, oxygen is the most abundant element at the surface of the Earth. In combined form it is found in ores, earths, rocks, and gemstones, as well as in all living organisms. Oxygen is a gaseous chemical element in Group VA of the periodic table. The chemical symbol for atomic oxygen is O, its atomic number is 8, and its atomic weight is 15.9994. Elemental oxygen is known principally in the gaseous form as the