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

The smallest particle of an element that retains its characteristics is called an atom. An atom is the basic building block of matter and retains the chemical properties of the element. Each atom consists of a nucleus containing protons and neutrons, surrounded by electrons. The specific arrangement and type of these subatomic particles determine the element's unique properties, such as its reactivity and bonding behavior.

Understanding that an atom is the fundamental unit helps clarify why it is distinct from other options. Molecules are made up of two or more atoms bonded together, which means they represent combinations of elements rather than the smallest form of a single element itself. Ions are atoms or molecules that have gained or lost one or more electrons, resulting in a charge, and thus do not represent the unaltered form of an element. Compounds are substances formed when two or more different elements chemically combine, which also shows that they are made of multiple atoms rather than depicting the smallest unit of a single element.

Thus, recognizing the atom as the smallest unit that retains the distinct attributes of an element is key in both chemistry and physics.