The smallest unit of an element that retains its properties.

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

Answer: (A)

The smallest unit of an element that retains its properties is the atom. An element’s chemical behavior comes from the electrons arranged around a central nucleus of protons and neutrons; the atom as a whole carries those properties. If you look at just the nucleus, you’re left with just nuclear particles that don’t determine how the element behaves in chemical reactions. A molecule is made of two or more atoms and can have properties not seen in the element itself, while an ion is the same atom with a charge, which can change some properties but still does not represent a smaller unit than the atom. Thus, the atom is the basic unit that preserves the element’s identity and properties.