A) How long will it take for 40.0 grams of Radium-226 (Ra-226) to decay to leave a total of 2.5 grams of Ra-226? Ra-226 has a half-life of 1600 years.


B) If there are 80.0 grams of Neptunium-240 (Np-240), how much Neptunium-240 will remain after 4 hours? The half-life of Neptunium-24 is 1 hour.