Ozone

Overview:
Ozone (O3) is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic O2. Ground-level ozone is an air pollutant with harmful effects on the respiratory systems of animals. Ozone in the upper atmosphere filters potentially damaging ultraviolet light from reaching the Earth's surface. It is present in low concentrations throughout the Earth's atmosphere. It has many industrial and consumer applications. Ozone, the first allotrope of a chemical element to be recognized by science, was proposed as a distinct chemical compound by Christian Friedrich Schönbein in 1840, who named it after the Greek word for smell (ozein), from the peculiar odor in lightning storms.[1][2] The formula for ozone, O3, was not determined until 1865 by J.L.Soret and confirmed by Schönbein in 1867.[1] The odor from a lightning strike is from ions produced during the rapid chemical changes, not from the ozone itself.[3]

Properties:
Ozone is a pale-blue poisonous gas with a sharp, irritating odor. Most people can detect about 0.01 ppm in air. Exposure to 0.1 to 1 ppm produces headaches, burning eyes, and irritation to the respiratory passages.[4]

At -112 °C, it forms a dark blue liquid. At temperatures below -193 °C, it forms a violet-black solid.[5]

-Facts taken from Wikipedia-