Oxygen (O) is a chemical element with atomic number (Z) 8, group 16 (Chalcogens), period 2, and atomic weight 15.999. The Oxygen (O) is a highly reactive non-metallic element and oxidizing agent that readily forms compounds with most elements. The Earth’s crust, one fifth (in volume) of the air is oxygen. Non-combined gaseous oxygen normally exists in form of diatomic molecules, O2, but it also exists in triatomic form, O3. (Refer to the Chemical Element; Periodic Table)
Related Definitions in the Project: The Element and Substance
