ATOMS are very, very small. They are the basic units of elements. Examples of elements are iron (symbol Fe), oxygen (symbol O), hydrogen (symbol H) and carbon (symbol C). Atoms are made of protons, neutrons* and electrons. Molecules are formed when two or more atoms are joined together. Common examples of molecules are water (H2O) and carbon dioxide (CO2).
* one isotope of one particular element has no neutrons. Do you know which one?
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