Learn About Atoms and Molecules for Kids

The atom is the building block for all matter in the universe. Atoms are extremely small. Atoms join together to form molecules. A drop of water contains billions of water molecules. Atoms are made up of even smaller particles called electrons, protons, and neutrons.

Protons, Neutrons, Electrons make up

Atoms which make up

Molecules

There are different kinds of atoms. The number of electrons, protons, and neutrons an atom contains determines the kind it is. These different kinds of atoms are called elements. These elements are listed on the periodic table.

There are only about one hundred types of atoms, but they make up millions and millions of different types of substances. This is because these atoms can join together in different ways to form lots of different types of molecules.

Atoms are made up of smaller particles called protons, neutrons, and electrons. The center of an atom is called the nucleus. The protons and neutrons reside in the nucleus. Electrons reside in orbits around the nucleus.

Protons have a positive charge, electrons have a negative charge and neutrons don't have a charge.

The periodic table arranges elements in order based on what is called their atomic number. It has rows and columns. The table was created by Russian scientist Dmitri Mendeleev (1834 - 1907) when he wrote his textbook Principles of Chemistry.

There is an element called Md (Mendelevium) named after him.

When two or more atoms join together they make up a molecule. Everything, including you, is made up of molecules. We are made up of trillions of molecules. When different types of atoms join together into molecules they are called compounds. Water is a compound you are very familiar with.

Water is made up of 2 hydrogen atoms and 1 oxygen atom. This is why it's also called H₂O. Hydrogen on it's own is an explosive gas. However, when two atoms of hydrogen join with an atom of oxygen, you get something that's safe to drink.

Atoms can join together like Lego blocks. They are held together by bonds. There are different types of bonds that hold atoms together.

• Covalent Bond
• Ionic Bond
• Metallic Bond

Atoms bond with other atoms to form molecules. For example, when two atoms of hydrogen bond with one atom of oxygen a water molecule is formed.

Atoms are so tiny, they can't be seen with the naked eye. Scientists use microscopes to see tiny things. However, atoms are so small, they also can't be seen with regular microscopes. A special type of microscope called a scanning tunneling microscope (STM) is needed. Scientists don't look into this microscope to see atoms. Instead, they are shown on a computer.

You will see from this list that some molecules are made up of only one element while others have several elements.

• Carbon dioxide CO₂ - one carbon atom, two oxygen atoms
• carbon monoxide CO - one carbon atom, one oxygen atom
• Glucose C₆H₁₂O₆ - six carbon atoms, twelve hydrogen atoms, six oxygen atoms
• Hydrogen peroxide H₂O₂ - two hydrogen atoms, two oxygen atoms
• Methane CH₄ - one carbon atom, four hydrogen atoms
• Ozone O₃ - three oxygen atoms
• Sodium chloride (salt) NaCl - sodium, chlorine
• Sulfur dioxide SO₂ - one sulfur atom, two oxygen atoms
• Water H₂O - two hydrogen atoms, one oxygen atom