A chemist makes 380. mL of magnesium fluoride (MgF2) working solution by adding distilled water to 20.0 mL of a 18.8 L stock solution of magnesium fluoride in water. Calculate the concentration of the chemist's working solution.

Round your answer to 3 significant digits

beta decay is the answer

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.