a. What is meant by the term 'half-life'? Calculate what fraction of a radioisotope would

remain after three half-lives?

b. An isotope of technetium, technetium-99, has a half-life of 6 hours. A hospital has a sample

which contains 36 mg of technetium-99. Calculate how much technetium-99 will be in this

sample after 12 hours.

c. Plutonium-238 is used in spacecraft to provide heat to power generators. One of these

generators contains 925 g of plutonium-238 when it is manufactured. Given that the half-life

of plutonium-238 has a half-life of 87.7 years, calculate the mass of plutonium-238

remaining after 200.0 years.