Final answer:
He (helium) is not an example of a molecule because it exists as individual atoms rather than being bonded to other atoms. In contrast, Cl₂, H₂, and CH₄ are all examples of molecules because they consist of multiple atoms bonded together.
Step-by-step explanation:
The option that is not an example of a molecule is D) He. A molecule is a group of two or more atoms bonded together, which means that they share or exchange electrons. Examples of molecules include H₂O (water), NH₃ (ammonia), and CH₄ (methane), where multiple atoms are held together by covalent bonds. On the other hand, He (helium) is an inert gas with a stable electronic configuration and exists as individual atoms, not bonded to other atoms; hence it is not a molecule but an atomic element.
To further clarify:
A) Cl₂ represents a chlorine molecule consisting of two chlorine atoms.
B) H₂ represents a hydrogen molecule with two hydrogen atoms.
C) CH₄ represents a methane molecule composed of one carbon atom and four hydrogen atoms.
These are all true molecules as they consist of more than one atom chemically bonded together.