Ask students: "In this collection of atoms, are all the atoms of a given element exactly the same? Naturally occurring chemical elements are usually mixtures of isotopes, and so their atomic masses are weighted averages of the masses of the isotopes in the mixture." Let them explain that isotopes of an element have the same chemical properties but different weights. Distribute the Science Net Links lab packet, Isotopes of Pennies, to each student.Then you will find the number of each type of penny in your mystery sample, using the concepts you developed in the activity." On the first page of the lab packet, ask students to define the following terms in their own words: isotopes, mass number, and atomic number.At the end of the lesson, students will be asked to reflect upon and revise, if needed, these definitions.
Have students refer back to their answers to the question in the motivation.
Have students complete Isotopes of Pennies assessment sheet so that you can assess student understanding of the concepts in this lesson.
In the first part of the assessment, students apply what they have learned to various elements.
This lesson helps students build their understanding of the properties of matter, specifically it will help them understand that average atomic mass is not a simple average, but is weighted according to percent abundance.
Before working on this lesson, students should be familiar with the periodic table and should have had some basic instruction in the following concepts: isotopes, mass number, and atomic number.