another<>in<>a molecule$$$another<>in a molecule happens to<>atoms$$$another<>in a molecule happens to atoms during<>a substitution reaction$$$a molecule<>happens to<>atoms$$$a molecule<>happens to atoms during<>a substitution reaction$$$atoms<>during<>a substitution reaction
Finally, the least one attacks another chlorine molecule to produce a sulfonyl chloride and a new chlorine atom which continues the reaction chain.
Replace another in a molecule happens to atoms during a substitution reaction.
What happens to atoms during a substitution reaction?