What substance is produced from ionization of clean dry air?

The ionization of clean dry air primarily produces ozone. When air is ionized, usually by an electric discharge such as a lightning strike or a high-voltage corona discharge, the natural components of the air—primarily nitrogen and oxygen—are excited to a state where they can react with each other.

Ozone (O₃) is formed when oxygen molecules (O₂) absorb energy and undergo a reaction that produces a triatomic form of oxygen. This reaction can be illustrated by the process where an oxygen molecule splits into two separate oxygen atoms, which can then recombine with other oxygen molecules to form ozone.

In a similar context, other gases such as chlorine, hydrogen, and nitrogen do not form as a direct product of ionizing air. Chlorine is typically produced from chemical processes involving salts or acids, hydrogen is produced from water or hydrocarbons through different chemical reactions, and nitrogen is a stable, non-reactive gas that does not undergo ionization in a manner that would lead to new compounds. Therefore, the most relevant and correct answer regarding the products of ionization of clean dry air is ozone.