What isotope is commonly used to determine thyroid activity and treat diseases of the thyroid? A) ¹¹C B) ⁶⁰Co C) ¹³¹I D) ⁹⁹Tc E) ¹⁰B

For each pair of elements listed, predict which one has more stable isotopes. (a) Ni or Cu (b) Se or Sb (c) Cd or Au

2.10 Which isotope in each pair contains more neutrons? (A) 35Cl or 33S, (b) 19F or 19Ne, (c) 63Cu or 65Zn, (d) 126I or 127Te

2.86 For some uses, the relative abundance of isotopes must be manipulated. For example, a medical technique called boron neutron capture therapy needs a higher fraction of 10B than occurs naturally to achieve its best efficiency. What would happen to the atomic weight of a sample of boron that had been enriched in 10B? Explain your answer in terms of the concept of a weighted average.