Question

what happens during the first step of ozone formation in atmosphere

Answer 1

Stratospheric ozone is formed naturally by chemical reactions involving solar ultraviolet radiation (sunlight) and oxygen molecules, which make up 21% of the atmosphere. In the first step, solar ultraviolet radiation breaks apart one oxygen molecule (O2) to produce two oxygen atoms (2 O) 

Answer 2

oxygen molecule breaks to give oxygen atom..
then the atom combine with oxygen molecule to give ozone.