What are molecules composed of?

Molecules are defined as combinations of two or more atoms that are bonded together, typically through covalent bonds. This bonding occurs when atoms share or transfer electrons, allowing them to achieve a more stable electronic configuration. Molecules can be made up of the same type of atoms, such as O2 (oxygen gas), meaning that they can consist of a single element. However, the fundamental characteristic that defines a molecule is the presence of at least two atoms, which is why the choice indicating that molecules are composed of two or more atoms is the correct answer.

Atoms, while being the building blocks of molecules, do not constitute a molecule by themselves unless they are bonded together with others. Additionally, while terms like "particles of energy" may refer to subatomic particles or various forms of energy, they are not relevant to the definition of a molecule. Thus, the correct understanding is that molecules are formed when two or more atoms come together, which aligns perfectly with the selected answer.