The question asks which free radical contributes to the depletion of the ozone layer. Let's analyze each of the given options:
\(NO\): Nitric oxide is a free radical that can contribute to ozone layer depletion through nitrogen oxides (NOx). However, its contribution is generally not as significant as halogens like chlorine.
\(Cl\): Chlorine radicals are well-known for their role in the depletion of the ozone layer. Chlorine atoms are highly reactive with ozone (\(\text{O}_3\)), resulting in a conversion to oxygen in a catalytic cycle:
Cl + \(\text{O}_3\) → ClO + \(\text{O}_2\),
ClO + \(\text{O}\) → Cl + \(\text{O}_2\).
\(OH\): Hydroxyl radicals can also react with ozone, but their effect is minor compared to chlorine radicals.
\(CH_3\): The methyl radical is not typically associated with ozone depletion.
Thus, the correct answer is Cl.
To summarize, chlorine radicals play a significant role in catalyzing the breakdown of ozone, explaining their impact on ozone layer depletion.
