Note: This video is designed to help the teacher better understand the lesson and is NOT intended to be shown to students. It includes observations and conclusions that students are meant to make on their own.
Students will again focus on the first 20 elements. Students will first look at a diagram and animation to understand the basic pattern of the arrangement of electrons on energy levels around an atom. Students will be given cards with information about the electrons and energy levels for each of the first 20 atoms. They will again try to correctly match the cards with each element.
Students will be able to interpret the information given in the periodic table to describe the arrangement of electrons on the energy levels around an atom.
Be sure that the 20 atom name cards are posted around the room. You will need the five cards on the right-hand side of each sheet. This lesson is intended as a follow-up to chapter 4, lesson 2.
Students can try playing the Periodic Table Game, Game #2. This is an online version of the periodic table card game from this lesson that you can assign as class work or homework after students have played the game in the classroom.
Print out the Element Cards and play the Periodic Table Game, Game #2.
Get the entire lesson plan and Student Activity Sheet for "Lesson 4.3 - The Periodic Table and Energy-Level Models."
Supplement in-class learning with interactive, multimedia-rich Google Forms lesson modules, perfect for reinforcing key chemistry concepts and scientific investigation skills.
Review with students that in lesson two they focused on the number of protons, neutrons, and electrons in the atoms in each element. In this lesson, they will focus on the arrangement of the electrons in each element.
Project the image Energy level cross-section.
Explain to students that electrons surround the nucleus of an atom in three dimensions, making atoms spherical. They can think of electrons as being in the different energy levels like concentric spheres around the nucleus. Since it is very difficult to show these spheres, the energy levels are typically shown in 2 dimensions.
Project the image Oxygen atom.
Tell students that this energy level model represents an oxygen atom. The nucleus is represented by a dot in the center, which contains both protons and neutrons. The smaller dots surrounding the nucleus represent electrons in the energy levels. Let students know that they will learn more about electrons and energy levels later in this lesson.
Have students look at the Periodic table of the elements 1–20 they used in lesson 2 to answer the following question:
Read more about The Periodic Table and Energy-Level Models in the Teacher Background.
Show students that you have 80 cards (4 for each of the first 20 elements). Before distributing the cards, explain that each card contains information about electrons and energy levels for the first 20 elements of the periodic table.
The students’ job is to read the card carefully, figure out which element the card is describing, and put the card at the spot in the room for that element. Remind students that they will need to count the electrons in order to identify each atom. Once students understand what their assignment is, distribute the cards to groups.
After all cards have been placed at the 20 different atoms, select two or three atoms and review whether the cards were placed correctly. This review will help reinforce the concepts about the structure of atoms and help students determine the number of protons and electrons in each atom.
Give each student a Periodic Table of Energy Levels activity sheet. This table contains energy level models for the first 20 elements. The electrons are included only for the atoms at the beginning and end of each period.
Download the student activity sheet, and distribute one per student.
The activity sheet will serve as the “Evaluate” component of each 5-E lesson plan. The activity sheets are formative assessments of student progress and understanding.
Project the Periodic table of energy levels and discuss the arrangement of electrons as students complete their activity sheet.
Project the image Periodic table of energy levels.
The image you project contains all of the electrons for elements 1–20. However, the periodic table on the activity sheet contains electrons only for the elements at the beginning and end of each period. Discuss the arrangement of electrons within the energy levels for these atoms and have students fill in the electrons for the other atoms.
Note: In the energy level diagrams, the electrons are spread out evenly in the level. Some books show them spread out this way and some show them in pairs. The pairing of electrons is meant to represent that pairs of electrons are in separate orbitals within each energy level. At the middle school level, it is not necessary for students to learn about electron orbitals. This information is offered so that it is clearer to you why electrons are often shown in pairs in energy level diagrams. An orbital defines a region within an energy level where there is a high probability of finding a pair of electrons. There can be a maximum of two electrons in each orbital. This is why the electrons are often shown in pairs within an energy level.
Tell students that the rows across on the periodic table are called periods.
Note: Students may wonder why an energy level can hold only a certain number of electrons. The answer to this is far beyond the scope of a middle school chemistry unit. It involves thinking of electrons as 3-dimensional waves and how they would interact with each other and the nucleus.
Continue to project the image Periodic table of energy levels for elements 1–20 and have students look at their activity sheets to find patterns in the number of electrons within each energy level.
Have students look at the periods (rows going across).
Number of energy levels in each period
How the electrons fill in the energy levels
A certain number of electrons go into a level before the next level can have electrons in it. After the first energy level contains 2 electrons (helium), the next electrons go into the second energy level. After the second energy level has 8 electrons (neon), the next electrons go into the third energy level. After the third energy level has 8 electrons (argon), the next 2 electrons go into the fourth energy level.
Note: The third energy level can actually hold up to 18 electrons, so it is not really filled when it has 8 electrons in it. But when the third level contains 8 electrons, the next 2 electrons go into the fourth level. Then, believe it or not, 10 more electrons continue to fill up the rest of the third level. Students do not need to know this.
Have students look at the groups (columns going down).
Tell students that the vertical columns in the periodic table are called groups or families. Ask students to compare the number of electrons in the outermost energy level for the atoms in a group. Students should realize that each atom in a group has the same number of electrons in its outermost energy level. For instance, hydrogen, lithium, sodium, and potassium all have 1 electron on their outer energy level. Let students know that these electrons in the outermost energy level are called valence electrons. They are the electrons responsible for bonding, which students will investigate in the next lesson.
Read more about The Periodic Table and Energy-Level Models in the Teacher Background.
