What is the smallest unit of an element that retains the property of the element?

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

Answer: (B)

The fundamental unit that defines an element is the atom. An atom carries the element’s identity, determined by the number of protons in its nucleus, and it is the smallest unit that can participate in the element’s characteristic chemistry. If you break an atom into smaller parts, you lose that elemental identity and its defining properties. A molecule is just a group of atoms bonded together and may not exhibit the element’s behavior in the same way as a single atom. An ion is still an atom, but with a different number of electrons giving it a charge, which is a variation of the same element rather than its smallest unit. Quarks exist inside protons and neutrons, not as the unit that defines an element. So the smallest unit that retains the element’s properties is the atom.