Which of the following particle diagrams best represents molecules of only one compound in the gaseous phase?

• A. A diagram showing a mixture of monatomic and diatomic particles.
• B. A diagram showing identical diatomic molecules evenly spaced throughout the container.
• C. A diagram showing clusters of three different types of molecules.
• D. A diagram showing both molecules and ions present in the container.

Answer: (B)

Verified step by step guidance

1. Understand that a compound consists of molecules made up of two or more atoms chemically bonded together in a fixed ratio and structure.
2. Recognize that in the gaseous phase, molecules of a single compound will be represented as identical particles evenly distributed throughout the container, reflecting the random motion and spacing typical of gases.
3. Identify that a diagram showing identical diatomic molecules (two atoms bonded together) evenly spaced represents a pure sample of one compound in the gas phase.
4. Note that diagrams showing mixtures (different types of particles, clusters, or ions) indicate multiple substances or phases, not a single compound.
5. Conclude that the correct diagram must show only one type of molecule, identical in composition and structure, dispersed evenly to represent a gaseous compound.