Final answer:
Helium-4 is the most stable among the listed isotopes because of its balanced neutron-proton ratio and the highest binding energy per nucleon, making it more stable than lithium-7, hydrogen-2, and carbon-12.
Step-by-step explanation:
The question asks which atom among lithium-7 (Li-7), helium-4 (He-4), hydrogen-2 (H-2, also known as deuterium), and carbon-12 (C-12) is most stable. In general, the stability of an isotope is determined by its binding energy, neutron-to-proton ratio, and presence in nature.
Helium-4 is known for its exceptional stability due to its balanced neutron-proton ratio and its status as a product of both nuclear fusion and radioactive decay processes.
Helium-4 is the most stable among the isotopes listed, being a doubly magic nucleus with two protons and two neutrons. It has the highest binding energy per nucleon, which makes it extraordinarily stable.
On the other hand, lithium-7 is also a stable isotope, but not as much as helium-4. Hydrogen-2 is stable but not as abundant as helium-4, while carbon-12 is a stable isotope and is used as a standard for atomic masses but falls short of helium-4's stability. Therefore, option B) Helium-4 is the most stable atom.
option B) Helium-4