Answer: Molecule
Explanation: A molecule is two or more atoms chemically joined together. If at least two different elements make up the molecule, it is called a compound. For example, hydrogen gas (H2) and water (H2O) are molecules, but water is also a compound because it is made up of hydrogen and oxygen. A molecule acts like a single unit and is the smallest piece of a substance that will retain all the properties of that substance. For instance, if you decomposed sugar (C12H22O11) to anything smaller than its molecular level, it would no longer be sugar. It would be individual carbon, hydrogen and oxygen atoms.
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