What is the smallest unit of a chemical element that retains its properties?

• A. Molecule
• B. Element
• C. Atom
• D. Ion

Answer: (C)

Atoms are the fundamental building blocks of elements, and the properties that define an element—its reactivity, bonding behavior, and place in the periodic table—come from a single atom’s structure and electrons. The smallest unit of a chemical element that still has the element’s identity and properties is that atom itself. Molecules are formed when atoms bond, so they reflect the properties of the whole group of atoms and aren’t the smallest unit that defines the element. An ion is an atom (or molecule) with a net charge, which alters its chemical behavior from the neutral element. An element describes the substance type defined by its atoms, not the unit itself. So the atom best fits as the smallest unit that retains the element’s properties.