We invite you to explore PBS LearningMedia™! or here.
After 2 resource views, you will be prompted to create an account.

## The Periodic Table of the Elements

Lesson Summary

### Overview

The periodic table is an essential part of any chemistry course. Its simple chart-like appearance belies the wealth of information that it contains. In this activity, students learn about the origin of the modern periodic table of elements and explore an interactive version that teaches them how to extract information from it. This activity is the first of three lessons.The Strange World of the Electron and Repeating Patterns: The Shape of the Periodic Table will help to further students' understanding of this powerful tool.

### Objectives

• Learn about the development of the periodic table of elements
• Be able to find information about specific elements in the periodic table

### Suggested Time

• One class period

### Part I: Origin of the Periodic Table

1. Describe or read the following summary of research on the structure of the atom:

• By the end of the nineteenth century, most scientists agreed on the existence of atoms and, thanks to the work of a physicist named J. J. Thomson, knew that these structures contained particles called electrons. Thomson proposed that the atom is a sphere filled with positively charged matter that contains negatively charged electrons embedded in it like plums in a pudding.

Today's "nuclear model" of the atom, first proposed by physicist Ernest Rutherford, is very different from Thomson's model. In it, the nucleus, which carries all of the positive charge and 99.9 percent of the atom's mass, is at the center of the atom. Orbiting at a distance of up to 100,000 times the diameter of the nucleus are the electrons. These tiny particles are anything but inconsequential, however. We now know that their arrangement and behavior is responsible for each element's unique set of chemical characteristics.

2. Distribute the Periodic Table of the Elements essay handout and have students read it. When they have finished, lead a discussion about how it was possible for Mendeleyev to develop a periodic table of elements before atomic structure, the essence of the table, was even known. (You might relate Mendeleyev's work to that of Gregor Mendel, who worked out the rules of simple genetics, or Charles Darwin, who described evolution by natural selection, both without specific knowledge of genes.)

### Part II: Anatomy of the Periodic Table

3. Ask students to work in pairs as they explore thePeriodic Table of the Elements interactive activity. Direct students to several sample elements within the interactive and identify the following information specific to each:

• The atomic number refers to the number of protons in the nucleus of the element's atoms. (Gallium, for example, has 31 protons.)
• The atomic mass increases as the atomic number increases, but unevenly. This is because the number of protons does not always equal the number of neutrons. The listed atomic mass is the average mass for all forms, or isotopes, of each element.
• The number of neutrons shown is the number for the most common isotope of the element.
• Electron configuration is the number of electrons found in each energy level of the element's atoms, starting from the innermost, or lowest, energy level.

4. Distribute copies of the Chemistry Scavenger Hunt (PDF) handout and allow 10 minutes for pairs of students to locate the missing information. You may create additional scavenger hunt entries -- this time with less starting information. Just be sure that at least one of the shaded columns is filled in to allow students to locate each element on the table.

### Check for Understanding

Ask students to work independently to create their own Chemistry Scavenger Hunt. Tell them to plan the table so that the left column symbols, when placed in order side by side, spell a word. The symbols for francium (Fr), iodine (I), carbon (C), titanium (Ti), oxygen (O), and nitrogen (N), for example, spell the word friction.

• For each element, have students fill in three or four columns, including at least one of the shaded columns.
• Have students exchange their Chemistry Scavenger Hunts with fellow students and complete them.

### Other Useful Materials

The ChemEd Digital Library has assembled a Resource Pack of materials on the Periodic Table, selected from a variety on NSDL Pathways.

Contributor:

Funder:

Producer: