The chemical element with atomic number 8 is oxygen. Oxygen has 8 protons in its nucleus, which defines its atomic number as 8. It is a nonmetallic element and is represented by the symbol "O" in the periodic table. Oxygen is essential for various biological and chemical processes, and it is the third most abundant element in the universe. It is commonly found in the Earth's atmosphere, water, minerals, and many organic and inorganic compounds.