In the history of atomic physics, electron, proton, and neutron were discovered respectively by which scientists?

Introduction / Context:
The discovery of subatomic particles was a major milestone in the development of modern atomic theory. Knowing which scientists discovered the electron, proton, and neutron helps trace the historical development of the atomic model from an indivisible sphere to a complex structure with a nucleus and electron cloud.

Given Data / Assumptions:
- The question asks specifically about the discoverers of the electron, proton, and neutron, in that order.
- Options list combinations of famous scientists from atomic theory.
- We assume standard school-level history of atomic structure.

Concept / Approach:
J. J. Thomson discovered the electron in 1897 through cathode ray experiments, showing that atoms contain small, negatively charged particles. Ernest Rutherford is credited with discovering the proton as a positively charged particle in the nucleus, especially through his work on alpha particle scattering and hydrogen nuclei. James Chadwick discovered the neutron in 1932 by analyzing radiation from beryllium bombarded with alpha particles, identifying a neutral particle in the nucleus.

Step-by-Step Solution:
Step 1: Recall that J. J. Thomson is associated with the discovery of the electron and the “plum pudding” model. Step 2: Remember that Ernest Rutherford's gold foil experiment led to the nuclear model of the atom and the identification of the positively charged proton. Step 3: Recognize that James Chadwick discovered the neutron, explaining the remaining mass in the nucleus. Step 4: Compare this correct sequence with the answer choices. Step 5: Choose the option listing Thomson, Rutherford, and Chadwick in that order.

Verification / Alternative check:
Atomic physics timelines and standard chemistry textbooks consistently list electron (Thomson, 1897), proton (Rutherford, early 1900s), and neutron (Chadwick, 1932). John Dalton and Niels Bohr played important roles in atomic theory, but they did not discover these three particles in the sequence asked.

Why Other Options Are Wrong:
Option B: John Dalton proposed an early atomic theory but did not discover subatomic particles; Niels Bohr developed a model of the atom with quantized energy levels.
Option C: This sequence is historically incorrect and mixes scientists with roles not matching the discoveries listed.
Option D: “None of the above” is wrong because one of the options correctly lists Thomson, Rutherford, and Chadwick as the discoverers of electron, proton, and neutron, respectively.

Common Pitfalls:
Students sometimes confuse Bohr's contribution (energy levels and spectral lines) with the discovery of particles. Another common error is to assume Dalton discovered everything related to atoms because he was an early proponent of atomic theory. Focus on the specific experimental discoveries to avoid this confusion.

Final Answer:
The correct answer is J. J. Thomson, Ernest Rutherford, and James Chadwick because they are historically credited with discovering the electron, proton, and neutron respectively.