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How can one chlorine atom destroy thousands of ozone molecules?

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ozone depletion — Ozone depletion The Antarctic ozone hole reaches its maximum extent in October of each year. On October 7, 2021, when this image was captured, the Antarctic ozone hole spanned 24.8 million square km (9.6 million square miles).

A single chlorine atom can destroy thousands of ozone molecules because it acts as a catalyst in a repeating chemical cycle within the stratosphere.12

The process begins when ultraviolet radiation breaks down human-produced chlorofluorocarbons (CFCs), releasing a free chlorine atom. This chlorine atom reacts with an ozone molecule ( $O_{3}$ ), stripping away one oxygen atom to form chlorine monoxide ( $C l O$ ) and oxygen gas ( $O_{2}$ ).12

Crucially, the cycle does not end there. Through a subsequent sequence of reactions, the chlorine monoxide is processed in a way that releases the original chlorine atom back into the atmosphere. Because the chlorine atom is regenerated rather than consumed, it is free to repeat this destructive process over and over again. This catalytic chain reaction allows a single chlorine atom to break apart thousands of ozone molecules before it is eventually removed from the stratosphere.2