What is the smallest particle of an element or compound that retains its chemical properties?

The smallest particle of an element or compound that retains its chemical properties is the atom. An atom is the basic unit of matter that defines the chemical elements. For instance, it is composed of protons, neutrons, and electrons, and it represents the fundamental building block that can combine with other atoms to form molecules. Each type of atom corresponds to a specific element on the periodic table and possesses unique chemical properties.

Molecules, while they are groups of two or more atoms bonded together and exhibit properties of compounds, are made up of atoms themselves. Therefore, the atom is the more fundamental unit. Similarly, ions are charged particles that result from the loss or gain of electrons by atoms, but they still consist of atoms and do not stand alone in terms of retaining the properties of the original element. Electrons are subatomic particles that make up atoms but do not constitute elements or compounds by themselves. Thus, understanding that an atom is the foundational unit that retains the individual properties of matter is key to recognizing its significance in chemistry.