What shows the kind, number, and arrangement of atoms in a molecule?

• A. Isomer
• B. Unsaturated Hydrocarbon
• C. Structural Formula
• D. Saturated Hydrocarbon

Answer: (C)

This question is about how we show exactly how a molecule is put together. A structural formula represents each kind of atom and exactly how many there are, and it also shows how those atoms are bonded to one another. That combination—which atoms are present and how they connect—gives the arrangement in the molecule, so this type of diagram directly communicates both composition and structure.

Other terms describe either different molecules with the same formula or different kinds of bonds within a class of compounds, rather than giving a single molecule’s actual map of connections. An isomer refers to another molecule with the same kinds and numbers of atoms but a different arrangement, while unsaturated and saturated hydrocarbons describe whether double/triple bonds exist or not, not the specific connectivity of atoms in a given molecule.