Which process decreases the number of nucleons in the nucleus by splitting it?

• A. Fusion
• B. Beta decay
• C. Ionization
• D. Fission

Answer: (D)

Splitting a heavy nucleus into two lighter nuclei is nuclear fission. This process involves the division of a nucleus into fragments, releasing energy and often neutrons in the process. Fusion does the opposite by combining light nuclei into a heavier one, increasing the nucleon content of the resulting nucleus. Beta decay changes a neutron to a proton (or vice versa) within the same nucleus and does not involve splitting the nucleus. Ionization removes electrons and leaves the nucleus unchanged. Remember, after fission the individual fragments have fewer nucleons than the original nucleus, but the total number of nucleons is conserved across all fragments.