Cobalt-60 has an atomic weight of 60.00 g/mol and a half-life of 5.260 years. If you start with a 1.000 gram sample of the
isotope, how much time will pass before you have just 0.100
grams of the isotope left?
a 16.44 years
b 18.44 years
C 17.47 years
d 14.77 years

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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.