Which statement best defines a molecule?

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A molecule is the smallest unit of a chemical substance that retains its characteristic properties and is formed when two or more atoms are held together by chemical bonds. This is why the statement describing two or more atoms bonded together and maintaining the substance’s distinct properties is the best fit. For example, water is a molecule because it consists of two hydrogen atoms and one oxygen atom bonded in a specific arrangement, giving it properties different from any of its constituent atoms. In contrast, a single atom by itself isn’t a molecule, since it’s just an individual element. A mixture of ions in solution isn’t a discrete molecule but a collection of separate ions dissolved in solvent. And a crystal lattice reflects how repeating units extend throughout a solid, describing the overall structure rather than a defined bonded unit that behaves as a single entity.