The simplest structural unit of an element or compound is a

• A. Molecule
• B. Molecular Compound
• C. Chemical Formula
• D. Electron-Dot Notation

Answer: (A)

The fundamental idea is that a molecule is the smallest unit that can exist and still retain the properties of a substance. When atoms bond together, they form a discrete entity that behaves as a single piece—the molecule. This applies to many elements, which exist as diatomic molecules like O2 or N2, as well as to compounds, where the molecule is the smallest unit containing the bonded atoms in a definite ratio. That’s why the molecule is the best choice here: it is the actual smallest unit that defines the substance’s identity.

A chemical formula is just a symbolic count of atoms, not a structure the substance would have on its own. Electron-dot notation shows valence electrons, not the unit itself. A molecular compound is a category describing a type of substance that forms molecules, not the fundamental unit.