What is the smallest particle that retains the characteristics of an element?

The smallest particle that retains the characteristics of an element is the atom. Atoms are the fundamental building blocks of matter and represent the smallest units of an element that still maintain the unique properties of that element. For example, a single carbon atom, with its specific number of protons, neutrons, and electrons, exhibits the chemical and physical properties associated with carbon.

Molecules consist of two or more atoms bonded together, but they can represent different substances. Compounds are made up of two or more different types of atoms chemically combined, which means they cannot be classified as single elements. Isotopes refer to variations of atoms of the same element that have different numbers of neutrons, altering their mass but not their elemental properties. Thus, it is the atom that serves as the defining structural unit of an element.