Which of the following is defined as a repeating unit found in many organic compounds, often determining their chemical properties?

• A. Isotopes
• B. Functional groups
• C. Radicals
• D. Ions

Answer: (B)

Verified step by step guidance

1. Understand the question is asking for a term that describes a repeating unit in organic compounds that often determines their chemical properties.
2. Recall that isotopes are atoms of the same element with different numbers of neutrons, which does not relate to repeating units in compounds.
3. Recognize that radicals are species with unpaired electrons, usually reactive intermediates, not repeating units.
4. Know that ions are charged species, either positive or negative, and are not considered repeating units in organic molecules.
5. Identify that functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules, and they often repeat in many organic compounds, defining their properties.