Supports up to 4 isotopes.
Most elements exist as a mixture of isotopes in nature. Copper has two stable isotopes: Cu-63 (62.930 amu, 69.17%) and Cu-65 (64.928 amu, 30.83%), giving an average of 63.546 amu. Tin has the most stable isotopes of any element — 10 — requiring all 10 to be included for an accurate average. The abundances must sum to 100%. If your result differs from the periodic table value, check that all major isotopes are included and abundances are current (IUPAC updates them periodically). Average atomic mass is crucial for converting between moles and grams in stoichiometric calculations.