Which particle is the smallest unit that retains the characteristics of an element?

The atom is the smallest unit that retains the characteristics of an element because it is the basic building block of all matter. Each element on the periodic table is defined by its number of protons, which are found in the nucleus of an atom. The arrangement of these protons, along with neutrons and electrons that orbit around the nucleus, determines the unique properties and behavior of that element.

In contrast, an electron, while a fundamental component of an atom, does not represent the entire element on its own. Molecules and compounds are formed when two or more atoms bond together, which means they can consist of multiple elements or a combination of elements and different types of atoms. Therefore, these larger structures cannot individually represent the distinctive characteristics of a single element. An atom, however, maintains the identity of the element it represents, making it the correct answer.