The definition of the principal energy level is contained in the Periodic Table by Energy Levels.

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Students will focus on the first 20 elements.To understand the basic pattern of electrons on energy levels around an atom, students will first look at a diagram and animation.The first 20 atoms will be given cards with information about the electrons and energy levels.They will try to match the cards with the elements.

Students will be able to read the periodic table to understand the arrangement of electrons around an atom.

When the activity is specified, download the student activity sheet and distribute one per student.The activity sheet will be part of the 5-E lesson plan.

The name cards of the 20 atom are posted around the room.There are five cards on the right hand side of each sheet.This lesson is a follow-up to lesson 2.

Students can play the Periodic Table Game in Lesson 4.3.After students play the periodic table card game in the classroom, you can assign homework or class work based on the online version of the game.

In lesson two they focused on the number of protons, neutrons, and electrons in the atoms.The electrons in each element will be the focus of this lesson.

Explain to students that electrons surround the nucleus of an atom in three dimensions.They think of electrons as being in the different energy levels around the nucleus.The energy levels are usually shown in 2 dimensions.

Students should be told that the energy level model represents an atom.The nucleus is represented by a dot in the center.There are small dots around the nucleus that show the electrons in the energy levels.Students will learn more about electrons and energy levels later in the lesson.

In lesson 2, students used the Periodic table to answer a question.

You have 80 cards for each of the first 20 elements.Explain that each card contains information about the first 20 elements of the periodic table.The students have to read the card carefully, figure out which element is being described, and put it in the room for that element.Students will need to count the electrons in order to identify each atom.Students should be given the cards to groups once they understand what their assignment is.

Pick two or three atoms and review whether the cards were placed correctly after all cards have been placed.Students will be able to determine the number of protons and electrons in each atom with the help of this review.

Each student should receive a Periodic Table of Energy Levels activity sheet.The table has models for the first 20 elements.Only the atoms at the beginning and end of each period are included with the electrons.

The electrons for elements 1–20 are contained in the image.The activity sheet only contains electrons 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.

The electrons are spread out evenly in the diagrams.Some books show them in pairs.The pair of electrons is supposed to show that electrons are in different parts of the energy level.Students don't need to learn about electron orbitals at the middle school level.This information will help you understand why electrons are shown in pairs in energy level diagrams and dot diagrams at the end of the chapter.A high probability of finding a pair of electrons is defined by an orbital.A maximum of two electrons can be found in each orbital.The electrons are shown in pairs because of this.

Students may wonder why an energy level has a certain number of electrons.The answer is not limited to a middle school chemistry unit.It involves thinking of electrons as waves that interact with each other and the nucleus.

Continue to project the 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.

A certain number of electrons go into a level before the next one.The next electrons go into the second energy level after the first one.After the second energy level has 8 electrons, the next electrons go into the third level.After the third energy level has 8 electrons, the next 2 electrons go into the fourth level.

The third energy level can hold up to 18 electrons, so it is not really filled when it has 8 electrons.The next 2 electrons go into the fourth level when the third level contains 8 electrons.10 more electrons will fill up the rest of the third level.Students don't need to know this.

Ask students to compare the number of electrons in the atoms in a group.Each atom in a group has the same number of electrons.All of them have a single electron on their outer energy level.Let students know that the electrons in the energy level are called valence electrons.Students will investigate the electrons in the next lesson.

In the periodic table, the atoms in the same column can react in a similar way.

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Students will see that the reactions are the same.Students can look at the periodic table to see how sodium and potassium are related.

Students will see that this reaction is different from the others.They can point out that calcium is in a different group than the other two.

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Show sodium reacting with acid.The acid is hydrochloric acid.nitric acid is what the HNO3 is.There are two different concentrations of the acid.Make sure students know that the sodium and potassium react in the same way.