Plutonium-236 is an alpha emitter with a half-life of 2.86 years. How long will it take for the 1.20 mg sample of Pu−236  to decay to 0.160 mg ?

Iodine-131 is an important radioisotope of iodine that has a radioactive decay half-life and is associated with medical diagnostic and treatment procedures. How many half lives does it take to reach 12.5 % of its original activity?

A moon rock collected by a U.S. Apollo mission is estimated to be 4.00 billion years old by uranium/lead dating. Assuming that the rock did not contain any lead when it was formed, what is the current mass of Pb206 in the rock, if it currently contains 1.430 g of U238? The half-life of U238 is 4.47×109 years.

Krypton-81m is used for lung ventilation studies. Its half-life is 13 ss. How long does it take the activity of this isotope to reach one-quarter of its original value?

Hydrogen-3 has a half-life of 12.3 years. How many years will it take for 502.0 mg ^3H to decay to 0.49 mg ^3H?

A radioactive sample has a decay constant of 1.32 x 10-3 h-1. What is its half life?

Strontium-89 is a beta emitter with a half-life of 50.6 days that is used in bone cancer treatment. How many days will it take for a 69.6 mg sample of Sr-89 to decay to 0.148 mg?​ (Assume no excretion of the nuclide from the body).