Readings

Isotopes and Average Atomic Mass

• Reading the following sections for chapter Chapter 4:

  • 4.18 Isotopes

  • 4.19 Atomic Mass Unit

  • 4.20 Calculating Average Atomic Mass 

Videos

Average Mass: Introduction

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 to Calculate Average Atomic 

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.

Practice Problems

Average Atomic Mass Problems

Use your calculator to find the average atomic mass each problem.