Which gas in Earth's atmosphere is responsible for the formation of ozone?

• A. Nitrogen (N2)
• B. Oxygen (O2)
• C. Methane (CH4)
• D. Carbon dioxide (CO2)

Answer: (B)

Verified step by step guidance

1. Understand that ozone (O3) is a molecule composed of three oxygen atoms bonded together.
2. Recall that ozone is formed in the Earth's atmosphere primarily through the interaction of oxygen molecules (O2) with ultraviolet (UV) light.
3. Recognize that when UV light strikes an oxygen molecule (O2), it splits the molecule into two individual oxygen atoms (O). This process is called photodissociation.
4. These free oxygen atoms (O) then react with other oxygen molecules (O2) to form ozone (O3) through the reaction: \(\mathrm{O} + \mathrm{O}_2 \rightarrow \mathrm{O}_3\).
5. Therefore, the gas responsible for the formation of ozone in Earth's atmosphere is oxygen (O2).