9. The identity of an element can be determined on the basis of which one of the following? A) The number of protons in an atom of the element.
B) The number of neutrons in an atom of the element.
C) The mass number of the element.
D) The atomic mass of the element.

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.

the objects have the same charge.