Atomic Weight

-On your periodic table silver has a weight of 107.9. The atomic mass of silver is 108. There is more than one isotope of silver and some are lighter than others.
a. 15.839% has a Mass Number of 107
b. 48.1161% has a Mass Number of 109
The element isn't split into half of the mass being 107 and 109 but it is intertwined together so it is difficult to separate. Uranium-238 is also difficult to separate.

To find the atomic weight for an element it is listed on your periodic table

24.305 would be the atomic mass for magnesium


54.938 would be the atomic weight for manganese