The smallest particle of an element that retains its identity in a chemical reaction is an atom.

Here's why:

* Atoms are the fundamental building blocks of elements. They are the smallest unit of an element that still possesses the chemical properties of that element.

* Chemical reactions involve the rearrangement of atoms. Atoms are not created or destroyed during a chemical reaction, they simply bond and unbond in different ways.

* Subatomic particles (protons, neutrons, electrons) do not retain the identity of the element. Changing the number of protons in an atom creates a different element entirely.

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