Radioactive rubidium-84 decays with a half-life of 37.1 days. (a) what is the value of k in s−1? 3.17e-7 incorrect: your answer is incorrect. s−1 (b) a sample contains 21.0 mg 84rb. how many decay events will be produced in the first second? assume that the atomic mass of 84rb is 84.0. decay events (c) a chemist obtains a fresh sample of 84rb and measures its radioactivity. she then determines that to do an experiment, the radioactivity cannot fall below 50.0% of the initial measured value. how long does she have to perform the experiment? days