Question

which best describes a chain reaction associated with a nuclear reaction?
neutrons released during a fusion reaction cause other nuclei to fuse.
neutrons released during a fission reaction cause other nuclei to split.
helium nuclei released during a fission reaction cause other nuclei to split.
helium nuclei released during a fusion reaction cause other nuclei to fuse.

Explanation:

To determine the correct option, we analyze nuclear chain reactions:

• In nuclear fission, a heavy nucleus splits, releasing neutrons. These neutrons can then strike other nuclei, causing them to also split, creating a chain reaction.
• Fusion reactions involve combining light nuclei (like hydrogen isotopes) to form heavier ones (like helium) and release energy, but they do not typically involve neutrons causing further fusion in a chain - like fission. Also, helium nuclei are products of fusion, not fission, and fission is about splitting, fusion about combining.
• Option 1: Fusion doesn't use neutrons to cause other nuclei to fuse in a chain (fusion is more about high - energy collisions of light nuclei).
• Option 2: In fission, neutrons released when a nucleus splits can hit other nuclei and make them split, which is the chain reaction in nuclear fission.
• Option 3: Fission releases neutrons, not helium nuclei, and helium nuclei are not involved in causing fission.
• Option 4: Fusion produces helium nuclei, and fusion is about combining nuclei, not splitting, so this is incorrect.

Answer:

B. Neutrons released during a fission reaction cause other nuclei to split.