Which element would you expect to have the largest radius based on the Periodic Table? Lead
Selenium
Chlorine

Lead

Explanation:

As you move down the periodic table, the elements get larger and gain additional electron shells, increasing the radius.  In order, they are on the table as Chlorine, Selenium, Lead.

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.