A freshly prepared sample of a certain radioactive isotope has an activity of 10.0 mCi. After 4.50 h, the activity is 7.80 mCi.
(a) Find the decay constant and half-life of the isotope?
(b) How many atoms of the isotope were contained in the freshly prepared sample?
atoms
(c) What is the sample's activity 30 h after it is prepared?
mCi