Krypton consists of several radioactive isotopes, some of which are listed in the following table.
Isotope .... Half-life
Kr-73 ...... 27s
Kr-74 ...... 11.5 min
Kr-76 ...... 14.8 h
Kr-81 ...... 2.1 x 105 yr
Which of these isotopes is most stable, and which isotope is “hottest”? How long does it take for 87.5% of each isotope to decay?