Identify the incorrect nuclear statement: which of the following is wrong based on basic atomic and nuclear physics?

Introduction / Context:
This question probes basic facts about nuclear particles and radiation. Spotting the incorrect statement requires recalling what gamma radiation is and how alpha particles and isotopic masses relate.

Given Data / Assumptions:

• Alpha particle identity.
• Relative masses of deuterium (≈2 u) and helium-4 (≈4 u).
• Nature of gamma radiation.
• Order-of-magnitude comparisons involving atomic vs nuclear scales.

Concept / Approach:
Gamma rays are high-energy photons (electromagnetic radiation), not electrons. High-energy electrons constitute beta-minus radiation. Alpha particles consist of two protons and two neutrons; when stripped of electrons, they are equivalent to He^2+ ions. Deuterium’s mass being roughly half of helium-4 is also consistent with atomic mass units.

Step-by-Step Solution:
Check (d): “Gamma rays are high-energy electrons” → incorrect; gammas are photons.Check (b): Alpha ≡ He nucleus → as a particle in matter, it corresponds to He^2+ (true).Check (c): Deuterium ~2 u vs helium-4 ~4 u → about half (true).Check (a): The density/scale contrast between nucleus and atom is enormous; 10^12 is an order-of-magnitude statement and acceptable for this context.

Verification / Alternative check:
Radiation taxonomy: alpha (He nuclei), beta (electrons/positrons), gamma (photons). Mass relations follow standard atomic masses.

Why Other Options Are Wrong:
(a), (b), (c) are broadly correct in the intended textbook sense.(d) misidentifies the nature of gamma radiation.

Common Pitfalls:
Confusing beta radiation with gamma; over-focusing on exact numeric ratios instead of order-of-magnitude reasoning for (a).

Final Answer:
Gamma rays are high-energy electrons.