In the periodic table, the element represented by the symbol 'O' is oxygen. Oxygen is a colorless, odorless gas essential for life on Earth, comprising approximately 21% of the atmosphere. It plays a critical role in respiration for most living organisms, allowing the release of energy from food through cellular respiration. Oxygen is also involved in various chemical processes, such as combustion and oxidation. As a highly reactive element, oxygen forms compounds with almost all other elements, prominently existing in water (H2O) and organic molecules. Its vital role makes it indispensable for life and science.