How many atoms are in 25.8 grams of Hg (mercury)

7.74568E22 or 7.74568 * 10^22 atoms

Explanation:

To find this, we first must find the moles of mercury in 25.8 grams. Since the molar mass of Hg is 200.59, we can find moles of Hg from 25.8 / 200.59 = 0.1286

To find the amount of atoms, we must multipy the amount of moles by Avagadro's number.

.1286 * 6.02214076 * 10²³ is 7.74568E22 or 7.74568 * 10^22 atoms

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.