Which of the following substances contributes to the depletion of the ozone layer in the atmosphere?

• A. Chlorofluorocarbons (CFCs)
• B. Carbon dioxide (CO2)
• C. Nitrogen gas (N2)
• D. Methane (CH4)

Answer: (A)

Verified step by step guidance

1. Understand that the ozone layer depletion is primarily caused by substances that release chlorine or bromine atoms in the stratosphere, which catalyze the breakdown of ozone (O3) molecules.
2. Recognize that Chlorofluorocarbons (CFCs) contain chlorine atoms and are stable enough to reach the stratosphere, where ultraviolet (UV) radiation breaks them down, releasing chlorine radicals.
3. Recall the key reaction where chlorine radicals react with ozone: \(\mathrm{Cl} + \mathrm{O}_3 \rightarrow \mathrm{ClO} + \mathrm{O}_2\), followed by \(\mathrm{ClO} + \mathrm{O} \rightarrow \mathrm{Cl} + \mathrm{O}_2\), which results in net ozone destruction.
4. Note that other substances listed, such as carbon dioxide (CO2), nitrogen gas (N2), and methane (CH4), do not release chlorine or bromine atoms and thus do not directly cause ozone depletion.
5. Conclude that among the given options, Chlorofluorocarbons (CFCs) are the substances responsible for ozone layer depletion due to their chlorine content and photochemical behavior in the stratosphere.