If an element named X has two isotopes, X-55 (55.93 amu, 55.1% abundance) and X-57 (56.9354 amu, 44.9% abundance), what is the average atomic mass of X?
Copper has two isotopes, Cu-63 (69.17% abundance and atomic mass 62.9296 amu) and Cu-65 (30.83% abundance and atomic mass 64.9278 amu). Calculate the average atomic mass of copper.
Which of these factors affect the average atomic mass of an element?