The smallest unit of an element that retains its chemical properties is called an ______.

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

Answer: (A)

Understanding what is the smallest unit of an element that keeps its chemical properties. An atom is the basic unit of an element. It contains a nucleus of protons and neutrons and electrons surrounding it. The chemical properties of an element—how it reacts, bonds, and interacts with other elements—are determined mainly by its electrons, especially the outermost ones. Because the atom carries the identity and characteristic behavior of that element, it is the smallest unit that retains those chemical properties. A molecule is formed when atoms bond and can have properties different from the individual element. An ion is a charged form of an atom (or group of atoms) that changes its chemical behavior compared to the neutral atom. The nucleus itself is just the center of the atom and doesn’t determine chemical behavior in reactions. So, the smallest unit that preserves the element’s chemical properties is the atom.