Nuclear stability insight: an element that has a comparatively large number of which constituents is most readily susceptible to nuclear fission under neutron bombardment?

Introduction / Context:
Nuclear fission behavior depends on nuclear composition and binding energy trends with mass and neutron-to-proton ratio. Heavier nuclei with relatively more neutrons tend to have lower binding energy per nucleon and are closer to instability thresholds, making them more susceptible to fission when perturbed by additional neutrons.

Given Data / Assumptions:

• We compare which constituent count (protons, electrons, neutrons) most favors fission.
• Typical reactor-relevant fission involves heavy nuclides (U-235, Pu-239) absorbing neutrons.
• External electron configuration is largely irrelevant to nuclear fission thresholds.

Concept / Approach:
Fission is governed by nuclear forces, not electronic structure. Heavy elements with high neutron numbers often have larger neutron excess (n − z), which can make the nucleus less tightly bound and more likely to split after absorbing another neutron. A high neutron count also reduces Coulomb repulsion issues since neutrons add to mass without adding charge, allowing heavy nuclei to exist but at the cost of increased propensity to fission under excitation.

Step-by-Step Solution:
Recognize that electrons do not determine nuclear fission susceptibility.Protons add Coulomb repulsion; too many protons without compensating neutrons destabilize but do not alone favor controlled fissionability.A relatively larger number of neutrons correlates with heavy, fissile or fertile nuclei that can undergo fission after neutron capture.Choose “Neutrons” as the controlling constituent in this qualitative comparison.

Verification / Alternative check:
Isotopes like U-235 and Pu-239 have substantial neutron excess compared with lighter elements. The capture of an additional neutron creates a compound nucleus at higher excitation that can overcome the fission barrier.

Why Other Options Are Wrong:
Protons: Excess charge increases Coulomb repulsion but does not alone favor induced fission readiness.Electrons: Atomic electrons are essentially irrelevant to the nuclear fission mechanism.Nucleons “in equal proportion”: Stable light nuclei are near 1:1; easy fission is a heavy-nuclei property with neutron excess.Positrons: Not nuclear constituents of stable matter.

Common Pitfalls:
Conflating chemical properties with nuclear stability; forgetting that fission is driven by nuclear composition and excitation energy, not electron shells.

Final Answer:
Neutrons