The smallest units of matter that retain the chemical properties of an element are called:

• A. protons
• B. molecules
• C. ions
• D. atoms

Answer: (D)

Verified step by step guidance

1. Understand the question is asking for the smallest units of matter that retain the chemical properties of an element.
2. Recall that protons are subatomic particles found in the nucleus of an atom, but alone they do not represent the smallest unit retaining chemical properties.
3. Recognize that molecules are combinations of two or more atoms bonded together, so they are not the smallest unit of an element.
4. Know that ions are atoms or molecules that have gained or lost electrons and carry a charge, but they are still based on atoms.
5. Conclude that the smallest unit of matter that retains the chemical properties of an element is an atom.