The mass of a single uranium atom is 4.70x10^-22 grams. How many uranium atoms would there be in 111 milligrams of uranium?

2.4 x 10²² atoms

Atomic mass is the average atomic mass of all its isotopes  

In determining the mass of an atom, as a standard is the mass of 1 carbon-12 atom whose mass is 12 amu  

So the atomic mass obtained is the mass of the atom relative to the 12th carbon atom  

mass single Uranium atom=4.7 x 10⁻²² g

then for 111 mg=0.111 g

uranium-238 i believe is your answer

put the answers   and i could answer.