What is the smallest unit of matter that still retains the properties of an element?

• A. Isotope
• B. An Atom
• C. Organelle
• D. Molecules and Atoms

Answer: (B)

The key idea is that elements are defined by their atoms, and the atom is the smallest unit that still shows the element’s characteristic chemical properties. An atom contains a nucleus and electrons arranged to give the element its typical reactivity and behavior. If you go smaller than an atom, you’d be dealing with subatomic particles that no longer define that element’s properties. Isotopes are just the same kind of atom with a different number of neutrons, so they’re still atoms of the same element. An organelle is a structure inside a cell, not a unit that defines elements. A molecule is made of atoms bonded together, so it’s not itself a single element. Therefore, the smallest unit that retains the properties of an element is the atom.