Final answer:
The smallest particle of matter that retains the properties of an element is an atom. Atoms are the fundamental building blocks of matter and are indivisible during chemical reactions.
Step-by-step explanation:
The smallest particle of matter that retains the properties of an element is known as an atom. These fundamental units are incredibly tiny, with tens of millions needed to span just one centimeter. All matter is constructed from atoms, and despite their minuscule size, they are the essential building blocks of the universe. Atoms of the same element share the same size, mass, and other characteristics, whereas atoms of different elements exhibit unique sets of these properties. It is also crucial to understand that atoms are indivisible in chemical reactions, meaning they cannot be created or destroyed.