We've all heard talk about Ozone, the ozone layer, products with ozone, etc.. But how many of us know what it really is?
The ozone molecule is basically three Oxygen atoms bonded together, as the figure shows below.
The arrow in the figure represents that the molecule "mutates" between the two existing forms (which are just mirror images in this case since the molecule only has one type of atom), in what is called Molecular Resonance. A pair of shared atoms keeps shifting from left to right, and right to left, changing the polarity of the molecule along with it. What we have in practical terms is not a single or a dual bond, but something like a "1.5" bond between the atoms. This makes it quite unstable and reactive. It will easily oxidize most metals, with the exception of Gold, Platinum and Iridium.
One of the most interesting aspects of it is the duality of being essential to life but also harmful to it.
As we all know, ozone in the high layers of the atmosphere protects us from harmful amounts of ultra violet (UV) radiation emitted by the Sun. Without it, life as we know it wouldn't exist. It is formed by those very rays hitting the more common O2 molecules, and it can be destroyed in a number of ways. One of them involves the infamous chlorofluorocarbons (CFCs), resultant of many human industrial activities.
However in the lower levels of the atmosphere it can be quite harmful to living beings. The respiratory system suffers specially from being exposed to it even in small concentrations, and it can be specially troublesome for people with previous afflictions like asthma. It is becoming a problem in many modern cities; it is not directly created by cars or industries, but the sun can react with the byproducts of these and be at the origin of low level ozone which is classified as a pollutant. Health organizations recommend concentrations below 40 ppb (parts per billion), while there are big cities such as Mexico City with concentrations above 100.
This toxic aspect is not without benefit, though. It's being used as a disinfectant, deodorant (not body spray, don't worry), and even white cells in our organism produce it to fight foreign bodies such as bacteria.
All in all, Ozone is like one of those superheros that protect people but are utterly obnoxious to be around. Sort of like Wolverine. Ozolverine.