What is atomic mass? It is a weighed average of the different isotopes of an element. It is sometimes referred to as atomic weight, relative atomic mass, or average atomic mass. We look at how to calculate and determine the weighed average of elements using atomic mass units.

How do you calculate atomic mass? You have to multiply the atomic weight of an atom (in amu, or atomic mass units) by the percent abundance expressed as a decimal. Then you add these together for all the isotopes of an atom.

How do you determine and calculate isotope abundance when you know the relative atomic mass (also known as atomic weight), as measured in amu or atomic mass numbers? Here we will go through the algebra and reasoning to figure out the amount of abundances of the isotopes, in percentages and in decimals.

If you're given the mass of each isotope of an element, and the average atomic mass, you can calculate the percent (%) abundance of each isotope. Let "x" be one of the abundances, and the other abundance is "1-x" ... then solve the equation using basic algebra.

Description: An example problem demonstrating how to calculate the mass of a specific isotope given the natural abundance of the isotopes and one isotope mass.