Question: where is most of an atoms mass found
[{'answer': 'the nucleus', 'provenance': [{'wikipedia_id': '19604151', 'title': 'Atomic mass', 'start_paragraph_id': 1, 'start_character': 230, 'end_paragraph_id': 1, 'end_character': 241, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '19604151', 'title': 'Atomic mass', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 447, 'bleu_score': 0.6915701935864731, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6727819327056165459}, 'section': 'Section::::Abstract.'}]}]