This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
[{'content': 'Ion which scatters X-ray most is - \nSelect and explain. \nA. Ca++, B. Hg, C. Pb, D. H+', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The scattering is proportional to the outer shell electrons available in the medium.\n\ni)\xa0Calcium has 2 electrons in the outer shell. But the option is calcium ion (Ca++), that means, it has donated both electrons, i.e. Ca++\xa0ion has no outer shell electron.\nii)\xa0Mercury has 2 electrons in the outer shell.\niii)\xa0Lead has 4 electrons in outer shell\niv) H+\xa0ion has no electron in outer shell as it has donated the only electron of its outer shell.\n\nAmongst the given options lead has maximum electrons in its outer shell. Therefore, the lead will cause maximum scattering of X-rays.', 'role': 'assistant'}]