What Is a Compound? - Lesson for Kids

Lesson Transcript
Rachel Torrens

Rachel obtained a Bachelor of Science in Biology from Grove City College. She then earned her Bachelor's and Master's Degree in Nursing from Thomas Jefferson University. For over 8 years, Rachel has practiced as a Board Certified Family Nurse Practitioner, and taught science to elementary aged students.

Expert Contributor
Laura Pennington

Laura received her Master's degree in Pure Mathematics from Michigan State University, and her Bachelor's degree in Mathematics from Grand Valley State University. She has 20 years of experience teaching collegiate mathematics at various institutions.

Investigate a special type of molecule called a compound. Discover what components determine compounds, learn how compounds fit under the umbrella of molecules, and explore common examples of compounds in daily life. Updated: 01/04/2022

Molecules or Compounds

Chemistry is a really cool field of science, but it involves learning a lot of vocabulary. This can be daunting when you're first starting to explore chemical reactions. For example, you've probably heard of molecules and compounds, but how exactly are they different?

A molecule is when two or more elements are chemically bonded together. A compound is two or more different elements chemically bonded together. Wait, what?

Try re-reading the last paragraph, and see if you can pick up on the difference between the two terms. Got it? Here's the major difference: a compound has two or more DIFFERENT types of elements bonded together. As you know, there are 118 elements on the periodic table. To have a compound, there needs to be at least two of these elements. Let's look at some examples.

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  • 0:04 Molecules or Compounds
  • 0:47 Everyday Examples
  • 2:21 Umbrella Term
  • 3:05 Lesson Summary
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Everyday Examples

Believe it or not, compounds are all around us. Simply turn on your faucet and water will come pouring out. Water's chemical formula is H2 O, which means there are two hydrogen atoms bonded to one oxygen atom. So, is water a compound? Let's run down the checklist: Are there two different types of elements in water? Yes! Hydrogen and oxygen. Therefore, water is a compound.

Ready for another one? Alright, look at your kitchen table and find the salt shaker. Table salt's chemical name is sodium chloride and is represented in formula form as NaCl. There is one atom of sodium (Na) chemically bonded to one atom of chloride (Cl). Again, we have two different elements joined together, and thus table salt is considered a compound.

You are doing great. Take a big breath in, and exhale it. Okay, so you just blew a compound out of your mouth! The air that comes out of your mouth when you exhale contains carbon dioxide, and carbon dioxide's chemical formula is CO2 because there is one carbon atom bonded to two oxygen atoms. Because carbon dioxide is made up of two different types of elements, carbon and oxygen, it is considered a compound.

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Additional Activities

Card Game Activity for Practicing with Elements, Compounds, and Molecules:


  • A molecule is formed when two or more elements are chemically bonded together.
  • A compound is formed when two or more different elements are chemically bonded together.

Materials Needed:

  • 118 note cards with the 118 elements from the periodic table on them
  • A piece of paper and a pencil

Steps to the Game:

  1. Mess up the note cards face down in a pile.
  2. Draw 3 cards, and record them or just place them face up in front of you.
  3. Write down three compounds or molecules that you can think of that can be made from the cards chosen, and explain why it is a compound or a molecule.
  4. Repeat as many times as desired.

Examples and Practice Questions:

  1. Suppose the cards drawn are sodium (Na), chloride (Cl), and hydrogen (H), and the list you come up with is salt (NaCl), molecular hydrogen (H2), and sodium hydride (NaH). Which of these are compounds, and which are molecules? Explain.
  2. Suppose the cards drawn are hydrogen (H), oxygen (O), and iron (Fe), and the list you come up with is water (H2O), two oxygen atoms (O2), and iron oxide or rust (Fe2O3). Which of these are compounds, and which are molecules? Explain.


  1. Salt (NaCl) contains two different elements, sodium and chloride, so it is a compound. Molecular hydrogen (H2) contains two atoms of the same element of hydrogen. Since H2 contains two or more elements, but the elements are not different, molecular hydrogen is a molecule. Sodium hydride (NaH) is made up of two different elements, sodium and hydrogen, so NaH is a compound.
  2. Water is made up of two different elements, 2 hydrogens and 1 oxygen, so H2O is a compound. Two oxygen atoms (O2) are two elements, but they are the same element, so O2 is a molecule. Iron oxide (Fe2O3), or rust, is made up of two different elements, 2 irons and 3 oxygens, so Fe2O3 is a compound.

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