
Determine the topic of the question-answer pair.
Question: "what naturally occurring isotopes does cobalt have?";  Answer: "Naturally occurring cobalt (Co) is composed of 1 stable isotope , 59Co. 28 radioisotopes have been characterized with the most stable being 60Co with a half-life of 5.2714 years, 57Co with a half-life of 271.79 days, 56Co with a half-life of 77.27 days, and 58Co with a half-life of 70.86 days."? Topic: 