Answer to Question #268702 in Atomic and Nuclear Physics for Mthokozisi Madlala

Question

Cobalt-60 has a half-life of approximately 5 years. If there was one microgram present in a sample originally, how many atoms would have decayed after 20 years?

Answer 1

$N=\frac mMN_A(1-2^{-\frac tT})=9.4\cdot 10^{18}.$