What Is A Molecule? Atoms And Molecules For Kids
Edition 2026-10
Atoms are the bricks. Molecules are what you build with them.
The short answer
A molecule is two or more atoms held together. Water is a molecule of two hydrogen atoms and one oxygen atom. Atoms are the building blocks; molecules are what you build with them.
The Long Answer
Everything you can touch is made of atoms. There are 118 known kinds, called elements, and about 90 of them are found in nature. When atoms join together, they make molecules.
A molecule can be made of one element: the oxygen you breathe is O2, two oxygen atoms joined. Or it can mix elements: carbon dioxide, CO2, is one carbon atom and two oxygen atoms. A molecule with at least two different elements is called a compound.
Atoms are almost unimaginably small. A single glass of water holds more atoms than there are glasses of water in all of Earth's oceans.
Atoms are made of even smaller pieces: protons and neutrons in a tiny nucleus, with electrons around it. Most of an atom is empty space. The smallest things anyone has found, electrons and quarks, have no size anyone has been able to measure.
Sources
- OpenStax Anatomy and Physiology: elements and atoms
- NIST: the Avogadro constant
- CERN: the Bohr model
- NOAA: How much water is in the ocean?
- Royal Society of Chemistry: Carbon
- USGS: graphite
- The size of the electron (arXiv)
- US Department of Energy: electrons
- IUPAC: names of elements 113, 115, 117 and 118
- LibreTexts Chemistry: the elements
It is on the poster
Atoms And Molecules Poster
What everything is made of.
$35 18x24$45 24x36
Reads alone from about 8
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