Introduction to Atoms


Introduction to Atoms teaches students about the difference between an atom and a molecule. Students will discover how these tiny objects create every element and molecule that exists in the world. They will learn to define the different parts of an atom and know their functions.

The “Options for Lesson” section has several additional suggestions of activities you can incorporate into the lesson. One suggestion is to have students create more than just one atom for the activity. You could also have students draw 2D models of atoms using poster board, markers, colored pencils, and other supplies.

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What our Introduction to Atoms lesson plan includes

Lesson Objectives and Overview: Introduction to Atoms teaches students about the building blocks of life. Students will learn about the parts of an atom and about the basic atomic structure of elements. They will also discover and be able to explain the difference between atoms and molecules. This lesson is for students in 4th grade and 5th grade.

Classroom Procedure

Every lesson plan provides you with a classroom procedure page that outlines a step-by-step guide to follow. You do not have to follow the guide exactly. The guide helps you organize the lesson and details when to hand out worksheets. It also lists information in the yellow box that you might find useful. You will find the lesson objectives, state standards, and number of class sessions the lesson should take to complete in this area. In addition, it describes the supplies you will need as well as what and how you need to prepare beforehand.

The list of supplies you will need for this lesson includes pencils, pens, highlighters, and a number of materials for the activity. The activity involves making models of various molecules. The supplies include Styrofoam balls, paint, small wooden dowel rods, a marker, and liquid glue.

Options for Lesson

The “Options for Lesson” section of the classroom procedure page lists several suggestions for additional activities or alternative ways to go about the lesson. A few of these suggestions relate to the activity. For example, you could pair students rather than have them work alone for the activity. You could also use additional materials for the models and have students create models of more than one chemical. You can assign a specific chemical to each student to model. As an alternative to the activity, you could have students make 2D models instead, using poster board and other drawing supplies. Several universities have online games that simulate how atoms and molecules are made. The section lists two websites with fun games the students could play during the lesson or after they complete the activity.

Teacher Notes

The teacher notes page provides a paragraph of additional information or guidance as you prepare your lesson. It suggests you teach this lesson in conjunction with others that relate to atoms, such as Molecules and Matter. You could also show the video about Atoms on the Learn Bright website. Use the lines on this page to write down thoughts or ideas you have before presenting the lesson to your students.


Mass and Density

The Introduction to Atoms lesson plan includes four pages of content. The first page explains the concept of matter. Objects are all around us, some solids like walls and furniture, some liquids like water and soft drinks, and others gases like the air we breathe. All of these things, along with all other objects in the world, are matter. Matter is anything that has weight and takes up space, even air. And atoms make up all the matter in the universe.

Students will then learn about how to measure such small particles. Weight, composition, and other measurements are all important when describing objects. Another word for weight is mass. Mass is the amount of material that makes up an object. A ping pong ball, for instance, has less mass than a basketball. The size of an object does not directly relate to its mass, however. A baseball is smaller than a basketball but has a greater mass. This is because baseballs have a higher density.

Density measures how much matter takes up a given space. Something very dense has a lot of atoms packed into a small space. So objects that are solid are more dense than gases. But within the same category of solids, the lesson compares a bar of gold to a bar of lead of the same size. Surprisingly, the gold bar weighs more than the lead one because gold is a denser metal even though lead has more mass.

Scientists determine the mass of an atom by using atomic numbers. Atoms are so tiny that we have to use special equipment to see them. Therefore, scientists can’t measure them with a regular scale or ruler. Instead, they use atomic numbers to describe an atom’s relative size and weight. The atomic number tells us how many protons are in each atom. The higher the atomic number, the more mass that atom has.

Facts about Atoms

The lesson provides a list of facts about atoms, somewhat like a summary of information students will find useful. All atoms contain three types of particles: protons, neutrons, and electrons. Protons have a positive electrical charge, and electrons have a negative electrical charge. Neutrons have no charge.

Protons and neutrons together form the nucleus of the atom. The nucleus is in the center of the atom, and the electrons spin around it. Nearly all the mass of an atom comes from the nucleus. This means that it is extremely dense. Yet, if an atom was the size of a football stadium, the nucleus would only be the size of a pea! Atoms are incredibly small. The average size is one-tenth of a billionth of a meter across. As tiny as they are, scientists have discovered that protons are actually made of particles called quarks, and electrons have leptons. That means these sub-particles are even smaller. Still, atoms are mostly empty spaces.

There are 92 naturally occurring atoms, meaning that we can find them in nature. Scientists have created some atoms in laboratories that wouldn’t exist otherwise. Nearly 74% of the atoms in the Milky Way Galaxy are hydrogen atoms. And when it comes to just the human body, scientists estimate that our bodies consist of 7 billion billion billion atoms. If that’s not crazy enough, the body replaces 98% of those atoms every year.

Atoms form elements, which are chemical substances that sometimes consist of only a single atom. Scientists developed a chart called the Periodic Table of Elements to help us keep track of all these different elements. Some atoms attach to other particles and create different chemicals and substances. For example, water is the result of two hydrogen atoms attached to one oxygen atom. This combination of elements is called a molecule, a piece of matter that contains more than one atom.

What Atoms Look Like

The lesson displays a diagram that resembles an atom. The protons are red and have plus signs on them to indicate their positive electrical charge. For the green neutrons, there are no symbols because they lack any charge. The electrons are blue and show a minus symbol to demonstrate a negative charge. They orbit around the proton and neutrons. The diagram shows lines that resemble electrons’ orbit, but those lines do not actually exist on a real atom. It’s very similar to how planets orbit the sun.

Because atoms have different numbers of protons and electrons (and neutrons), they don’t all look exactly the same. The numbers of these particles determine which element that atom is. Since molecules consist of multiple atoms or elements, the number of protons in each atom would help determine the molecule. For instance, if you find that a molecule has two hydrogen atoms and one oxygen atom, it would be a molecule of water.

The Periodic Table of Elements is a very useful tool when it comes to figuring out which atoms are which. The bottom of the page provides two boxes, one for carbon dioxide and the other for table salt. Students can try to draw what those two molecules would look like in the corresponding boxes. You can do it as a class or let students try on their own. The last page provides a Periodic Table for students to reference when they need it.

Key Terms

Here is a list of the vocabulary words students will learn in this lesson plan:

  • Matter—anything that has weight and takes up space
  • Mass—the amount of material that makes up an object
  • Density—how much matter is compacted in a space
  • Atomic number—the number that describes how many protons an atom has
  • Element—a chemical substance often made from a single atom
  • Molecule—a piece of matter that contains more than one atom


The Introduction to Atoms lesson plan has three worksheets: an activity worksheet, a practice worksheet, and a homework assignment. Each of these worksheets will help reinforce students’ comprehension of the lesson material in a different way. The activity in particular provides a hands-on opportunity for students to demonstrate their grasp of the concepts they learned about. The guide on the classroom procedure page outlines when to hand out each worksheet to the students.


For the activity, students will create a model of an atom. Supplies they will need to build it include Styrofoam balls, paint, and wooden dowel rods. The worksheet lists several common household cleaning chemicals, like baking powder and mouthwash. Students will choose an item from the list and create a molecule that matches the formula on the worksheet. If they choose salt, for instance, they will need to create a molecule that has one sodium atom and one chlorine atom. Every atom will be a different color so that students can distinguish among them. Students can also use a marker to label the atoms with their corresponding chemical symbol. A few of the chemicals have double asterisks next to them to indicate the possibility of building them as a class or small groups.


The practice worksheet includes two sections. First, students will label each of the four parts of an atom using the diagram on the right. Then they will read through a short paragraph about atoms and fill in 11 blanks. They cannot use the content pages for reference. Instead, they should see how many answers they get right.


Students may particularly enjoy the homework assignment, which requires them to get creative with superheroes and powers. The instructions describe how many superheroes get their powers from the elements that come from atoms. For this assignment, students will visit the website listed. Then they will choose an element from the Periodic Table of Comic Books. The bottom of the worksheet lists a few prompts. Students will answer the prompts about their superhero and then draw a picture to represent them.

Worksheet Answer Key

The lesson plan document includes answer keys for both the practice and homework worksheets. For the practice, students’ responses should mirror those of the answer key. Their responses on the homework assignment, on the other hand will vary. The goal is for them to learn about the elements in a fun way. Ensure you check their work for accuracy. If you choose to administer the lesson pages to your students via PDF, you will need to save a new file that omits these pages. Otherwise, you can simply print out the applicable pages and keep these as reference for yourself when grading assignments.

Additional information


4th Grade, 5th Grade


Science, Video

State Educational Standards


Lessons are aligned to meet the education objectives and goals of most states. For more information on your state objectives, contact your local Board of Education or Department of Education in your state.

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Introduction to Atoms

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