1. The problem statement, all variables and given/known data I'm a bit negative to this assignment, because I think this has lack of information. The question is: "220-Rn is radioactive and gives α-particles with the energy of 6.4 MeV. An injection of 0.25 µg Radon is performed in a closed container. How big effect is developed in the container immediately after the injection because of the α-radiation? 2. Relevant equations 220-Rn --> 220.0114 u --> Half life: 56 s 3. The attempt at a solution First I must determine the number of nucleus: 0.25 µg is 2.5*10^-16 kg. And the weight of one nucleus in kg is 220.0114*1.6605402*10^-27 = 3.65337774*10^-25 kg. Now, my weight of used nucleus divided by the weight of one: (2.5*10^-16)/(3.65337774*10^-25) = 684298251.6 pieces of 220-Rn. I was trying to multiply the number of nucleus by 931.49 MeV, but I know this was wrong. What I'm missing to be able to answer in Watts is over which time this energy was obtained. Anyone who agree? Maybe someone know how to solve this probably easy problem?