What is ozone? Ozone is a stable molecule O composed of three oxygen atoms While stable, it is highly reactive. The greek word ozein means to smell"and o3 has a strong pungent odor. Electric discharges in air often produce significant quantities of o3 and you may have smelled o3 near these sourcesWhat is ozone? Ozone is a stable molecule composed of three oxygen atoms. O O O While stable, it is highly reactive. The Greek word ozein means “to smell” and O3 has a strong pungent odor. Electric discharges in air often produce significant quantities of O3 and you may have smelled O3 near these sources