\n– Statement 1 is correct: Chlorofluorocarbons (CFCs) are very stable in the lower atmosphere (troposphere) and do not easily react or break down. Over time, they slowly migrate upwards through diffusion into the stratosphere.
\n– Statement 2 is correct: Once in the upper atmosphere (stratosphere), CFC molecules are exposed to high-energy ultraviolet (UV) radiation from the sun, which breaks the carbon-chlorine bond, releasing highly reactive free radical chlorine atoms (Cl\u2022). A chlorine radical then reacts with an ozone molecule (O\u2083) to form chlorine monoxide (ClO\u2022) and oxygen (O\u2082).
\n– Statement 3 is correct: The chlorine monoxide radical (ClO\u2022) is also highly reactive. It can react with a free oxygen atom (O) (which is naturally present in the stratosphere from the breakdown of O\u2083) to form another chlorine radical (Cl\u2022) and oxygen (O\u2082). The regenerated chlorine radical can then attack another ozone molecule, continuing the cycle. This chain reaction allows a single chlorine atom to destroy many thousands of ozone molecules before it is eventually removed from the stratosphere by other processes. This catalytic cycle leads to significant depletion of the ozone layer.
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