Mass number, on the other hand, is the count of protons and neutrons for any single isotope and is always an integer." Display a "collection of atoms" such as a beaker of a solution or a glass of milk. They are all listed in many places, including the websites used in this lesson." Remind students that ALL atoms are isotopes.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." Accept all answers and ask students to record their answers to this question in their science journals.
You may wish to collect these sheets to check for student understanding.
Scientists continue to investigate atoms and have discovered even smaller constituents of which electrons, neutrons, and protons are made.
According to research, students may at first take isotopes to be something in addition to atoms or as only the unusual, unstable nuclides.
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.
Students should be able to describe an atom and its basic structure.
Tell students: "In this activity, you will find weighted averages of the masses of two kinds of pennies.