Final answer:
The correct option is D. A molecule is formed when atoms of the same element bind together in a stable form.
Step-by-step explanation:
When atoms of the same element bind together in a stable form, they create what is known as a molecule. A molecule consists of two or more atoms that are chemically bonded together. While the term "molecule" is often associated with different elements combining, it is important to note that atoms of the same element can also form molecules under certain conditions.
For example, oxygen gas (O2) is a molecule composed of two oxygen atoms that are chemically bonded. Similarly, nitrogen gas (N2) consists of two nitrogen atoms bonded together. These diatomic molecules, formed by atoms of the same element, are stable and have distinct properties.
The options provided in your initial question—compound, isotope, and element—refer to different concepts. Compounds are substances formed when atoms of different elements chemically combine. Isotopes are variants of an element with the same number of protons but different numbers of neutrons. Elements, as mentioned earlier, are substances composed of identical atoms.
In summary, when atoms of the same element bind together, they create molecules, making option (A) Molecule the correct answer.