1. The graph above represents the nuclear decay of a radioactive element, measured using a radiation-detecting device. What is the half-life, in days, of this hypothetical element? 2. If the half-life of a given substance is 65 days, how long will it take for a 100-gram sample of the substance to decay until there is only 25 grams of the radioactive material remaining?
3. If a sample of radioactive isotopes takes 60 minutes to decay from 200 grams to 50 grams, what is the half-life of the isotope? Hint: First, determine how many times the sample has lost half of its mass, which tells you how many half-life cycles have occurred.
4. If a 500.0 g sample of technetium-99 decays to 62.5 g of technetium-99 remaining in 639,000 years, what is the half-life of technetium-99?