The chemical element with the atomic number 8 is oxygen (O). It is a vital element for life on Earth, primarily because it is essential for respiration in many living organisms. Oxygen is a colorless, odorless gas at room temperature and is highly reactive, forming compounds with most elements. It readily combines with other elements to form oxides and is a significant component of water (H₂O). The Earth's atmosphere contains approximately 21% oxygen, which is produced by photosynthetic organisms such as plants and algae, making it crucial for supporting life.