what is o2 in chemistry

Oxygen (O2) is a chemical element with the atomic number 8. It is a nonmetal and an essential element for human survival. Oxygen forms a diatomic molecule (O2) consisting of two oxygen atoms bonded together. It is a colorless, odorless gas and is the third-most abundant element in the universe, as well as the most abundant element on Earth. Oxygen is highly reactive and serves as an oxidizing agent, readily forming oxides with most elements and compounds. It is used by complex forms of life, such as animals, in cellular respiration.