What is described here is actually the formation of ozone in the atmosphere. Ozone is what makes up the ozone layer, the shield in the Earth’s atmosphere that absorb the sun’s harmful UV radiation.
Now when solar energy hits O2 molecules, this results to a release in Oxygen atoms. When these Oxygen atoms combine with O2 molecules, Ozone or O3 is formed.
The correct answers are:
Oxygen atoms
Ozone