Which of the following is/are TRUE of nuclear fission? I. A heavy nucleus is split into two nuclei of…

Analyze the question: We need to decide which statements correctly describe nuclear fission.

Concept:

• Nuclear fission is the splitting of a heavy nucleus (e.g. Uranium-235) into two smaller nuclei of comparable mass, usually with the release of neutrons and a large amount of energy.
• Nuclear fusion is the joining of two light nuclei to form a heavier one (e.g. hydrogen isotopes forming helium, as in the Sun).
• In both processes, energy is released because of the mass defect. The total mass of the products is slightly less than the total mass of the reactants. This lost mass is converted to energy according to E = mc².

Checking each statement:

• I. A heavy nucleus is split into two nuclei of comparable masses. TRUE. This is the definition of fission.
• II. Two light nuclei are joined together to form a heavier nucleus. FALSE. This describes fusion, not fission.
• III. The total mass of the products is less than that of the reactants. TRUE. The mass defect is converted to energy (E = mc²).

So statements I and III are true.

Answer: D (I and III only)

Tip: Remember "FISsion = SPLIT" (like a fissure or crack) and "FUsion = FUSE together". Mass decreases in both processes because the lost mass becomes energy, so statement III is true for both. Only the splitting versus joining statement separates them.