In this assignment, you will write and balance a chemical equation. Then, you will use a table of enthalpy values to calculate the energy change in the reaction. Next, you will create a model of the energy change
in the reaction. Finally, you will write an explanation that describes the energy change in the reaction.

the answer to your question is c

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.