AP Environmental Science

Answer: C - Ozone forms when atomic oxygen reacts with molecules of 0_2.

Key Takeaway: Ozone, known chemically as O₃, is what forms when atomic oxygen reacts with molecules of O₂ when oxygen that has absorbed ultraviolet radiation from the sun breaks apart, forming two atoms of oxygen that can then react with a molecule of oxygen. Much of the Earth’s ozone is formed in the tropics, where the sun is overhead for the majority of the year. The ozone is then distributed around the earth by wind. Ozone high in the atmosphere helps to protect the Earth from the sun’s ultraviolet rays.