An individual was injected with 80 mg of inulin and 960,000 counts per min (cpm) of tritium-labeled water (3H20) to determine the volume of various body fluid compartments. After equilibration a blood sample was obtained and the plasma inulin concentration was 0.5 mg% and the plasma activity (concentration) of tritium was 20 cpm/ml. The volumes of which body compartments can be determined?

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.