GO IN DEPTH

# Isotopes of Pennies Assessment Sheet

By Roman Oleinik (Own work) [CC-BY-SA-3.0], via Wikimedia Commons

### Introduction

Now you will apply what you have learned in the lesson Isotopes of Pennies by answering the questions on this sheet

Calculate the average mass of potassium if the abundance and atomic masses making up
its naturally occurring samples are:

Potassium-39 93.12% 38.964
Potassium-41 6.88% 40.962

Calculate the average mass of magnesium if the abundance and atomic masses making up
its naturally occurring samples are:

Magnesium –24 78.70% 23.985
Magnesium –25 10.13% 24.968
Magnesium –26 11.17% 25.983

The atomic mass of copper is 63.540 amu. It is composed of two isotopes, Cu-63 and Cu-
65, with atomic masses of 62.930 and 64.928 respectively. What is the relative abundance
(%) of these isotopes in naturally occurring samples of copper?

What is the difference between mass number and atomic mass?

Write a short summary explaining how this lab illustrates the concepts that you tried to
explain at the beginning of the lab. Have your explanations changed? If so, explain how.