Average atomic mass f 1 M 1 f 2 M 2 f n M n where f is the fraction representing the natural abundance of the isotope and M is the mass number weight of the isotope. Look up the element on a periodic table to check your answer. The average atomic mass is usually written underneath the.
Formula to calculate average atomic mass.
The means that when added together the abundances must equal one. Molecular mass or molar mass are used in stoichiometry calculations in chemistry. Average Atomic Mass Formula The following formula is used to calculate the average atomic mass of a substance. The average atomic mass of an element is the sum of the masses of its isotopes each multiplied by its natural abundance.