Two isotopes of iodine are commonly encountered in medical contexts: iodine-127, a stable isotope found in table salt, and iodine-131, a radioactive isotope used in thyroid imaging and therapy.
Answer the following, using complete sentences and appropriate reasoning grounded in atomic structure.
(a) State the number of protons present in every atom of iodine, and justify how that number is determined from its position on the periodic table.
(b) Determine the number of neutrons in an atom of iodine-127 and in an atom of iodine-131. Show your reasoning.
(c) Explain why iodine-127 and iodine-131 exhibit identical chemical behavior even though their nuclei differ.
(d) Discuss one physical property that differs appreciably between the two isotopes and describe how this difference is exploited in medical imaging or therapy.