Nature of transformations: radioactive decay should be classified as which type of change at the atomic scale?

Introduction / Context:
Understanding what distinguishes nuclear changes from chemical or physical changes is fundamental in radiochemistry and nuclear engineering. Radioactive decay alters the nucleus, not merely electron arrangements or phases of matter.

Given Data / Assumptions:

• Chemical changes involve electron-shell interactions forming/breaking bonds.
• Physical changes involve state, shape, or other macroscopic properties without altering atomic identities.
• Radioactive decay originates within the nucleus.

Concept / Approach:
In radioactive decay (alpha, beta, gamma), the composition or energy of the nucleus changes. The element may transmute (change Z), which cannot be achieved by purely chemical means. Thus, decay is a nuclear change; it may accompany emitted radiation and energy release but does not principally involve chemical bonding mechanisms.

Step-by-Step Solution:
Identify the locus of the transformation: nucleus vs electron cloud.Alpha/beta change the nucleus; gamma releases nuclear energy without changing Z or A.Therefore, classify as nuclear change.

Verification / Alternative check:
Transmutation examples (e.g., beta decay increasing atomic number by 1) confirm nuclear identity changes that are independent of chemical environment, pressure, or temperature.

Why Other Options Are Wrong:

• Chemical change: Involves electron-shell rearrangements, not nuclear transformations.
• Physical change only: Does not alter atomic identity.
• None of these/Electrochemical change: Do not capture nuclear processes.

Common Pitfalls:
Assuming decay rates can be significantly altered by chemical state; while tiny effects exist in special cases, decay is fundamentally nuclear.

Final Answer:
Nuclear change