Because these isotopes decay more slowly, they can be used to date much older specimens.

Having read the above passage, choose the right answer to the following question (choices are less useful isotope? or more useful isotope ):


For dating the age of a fossil, and compared to the isotope Francium with a 22 minute half-life, would Carbon 14 with its 5730 year half-life be a less useful isotope? or more useful isotope? 

