Acertain element x has four isotopes. 0.5600% of x has a mass of 83.91343 amu. 9.860% of x has a mass of 85.90927 amu. 7.000% of x has a mass of 86.90890 amu. 82.58% of x has a mass of 87.90562 amu. what is the average atomic mass of element x?

solution:

Find the average of atomic weight is

(0.0056 x 83.91343)+(0.098860 x 85.90927)+(0.07x86.90890)+(0.8258x87.90562)=87.61665 amu

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.