The element represented by 'O' on the periodic table is Oxygen. With the atomic number 8, oxygen is a vital element for life on Earth, as it is essential for the process of respiration in living organisms. Oxygen makes up about 21% of the Earth's atmosphere and is a key component of water (H2O), which is crucial for all known forms of life. In addition to its biological importance, oxygen is used in various industrial processes, including the production of steel, plastics, and other chemicals. Its reactive nature also allows it to form compounds with many other elements.