Iodine that enters the body is stored in the thyroid gland from which it is released to control growth and metabolism. The thyroid can be imaged if iodine-131 is injected into the body. In larger doses, I-133 is also used as a means of treating cancer of the thyroid. I-131 has a half-life of 8.70 days and decays by β− emission.
(a) Write an equation for the decay.
(b) How long will it take for 95.0% of a dose of I-131 to decay?
OpenStax Chemistry 2e, 21.5 Uses of Radioisotopes, exercise 3