Final answer:
The smallest particle of an element that retains its characteristics is an atom. An atom is composed of electrons, protons, and neutrons, with the number of protons defining the element's identity.
Step-by-step explanation:
The smallest particle of an element that retains the characteristics of the element is an atom. An atom is the fundamental unit of an element that exhibits the chemical properties of that element. While an atom is composed of subatomic particles such as electrons, protons, and neutrons, it is the entire atom that represents the smallest amount of an element with its unique characteristics intact. Electrons are negatively charged particles that revolve around the nucleus, protons are positively charged and reside in the nucleus providing each element its identity with their unique number known as the atomic number, and neutrons are neutral particles that also reside in the nucleus and contribute to the atom's mass along with protons.