sentence2_structure: 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
sentence1: A HYDROGEN BOND is the attraction of a hydrogen atom of one molecule to an atom of another molecule.
sentence2: Replace another in a molecule happens to atoms during a substitution reaction.
question: What happens to atoms during a substitution reaction?