For 10 points, name this gaseous allotrope of oxygen that forms a namesake layer in the atmosphere.
This chemical ages rubber by creating radicals that destroy polyisoprene chains. It is often used instead of chlorine to disinfect water, and this compound is continuously created through the Chapman cycle. The reaction forming it can be reversed through the catalytic use of free radicals such as nitric oxide, and the density of this compound can be measured using Dobson units. It is often found in the lower stratosphere, where it acts to absorb ultraviolet light. For 10 points, name this gaseous allotrope of oxygen that forms a namesake layer in the atmosphere.
This chemical ages rubber by creating radicals that destroy polyisoprene chains.
Ozone [accept O3]