An atom is the smallest unit of an element that retains the identity (and the chemical properties) of that element. + 66 others found this useful. Sandra Pinzon.Edit.he atom is the smallest particle of an element that retains it's characteristics. Sub-atomic particles such as protons, neutrons and electrons form the atom and it is the amo … unt of each of these sub-atomic particles that make the element that element. 5 people found this useful.