Why was the discovery of the neutron made relatively late compared to the discovery of other subatomic particles such as the electron and proton?

Introduction / Context:
This question belongs to atomic structure and modern physics. It asks why the neutron, discovered by James Chadwick in 1932, was identified significantly later than the electron and proton. Understanding this reason gives insight into how experimental detection of particles depends on their charge and interaction with fields.

Given Data / Assumptions:

• We are comparing the discovery timeline of the neutron with that of the electron and proton.
• Options suggest different possible reasons, such as location in the nucleus or absence of charge.
• We assume basic knowledge that neutrons are neutral, while electrons and protons are charged.
• The question asks for the main reason for the delayed discovery.

Concept / Approach:
Charged particles like electrons and protons interact strongly with electric and magnetic fields, so they leave clear signatures in many experimental setups, such as deflection in electric and magnetic fields. Neutral particles like neutrons do not experience electromagnetic forces, so they cannot be detected easily by standard methods based on deflection or ionisation by direct charge. Hence, discovering the neutron required more indirect experimental strategies involving nuclear reactions and scattering.

Step-by-Step Solution:
1) Electrons were discovered by J. J. Thomson using cathode ray experiments, which relied on the deflection of charged particles in electric and magnetic fields.2) Protons were identified as positively charged particles in canal rays, again detected due to their interaction with fields.3) Neutrons, on the other hand, have no electric charge, so they do not respond to electric fields and produce no direct ionisation trails in many detectors.4) Because of this neutrality, early experimental techniques could not easily detect or distinguish them from other radiation.5) Only when Chadwick carefully analysed nuclear bombardment experiments did he infer and confirm the existence of a neutral, massive particle, later named the neutron.

Verification / Alternative check:
Historical accounts show that scientists earlier suspected some neutral mass within the nucleus because atomic mass exceeded what could be explained by protons alone. However, there was no direct experimental evidence until neutron scattering experiments in beryllium and paraffin produced effects not explainable by known charged particles. The absence of charge was the central difficulty, as detection instruments of that era were mostly sensitive to charged radiation through deflection or ionisation patterns.

Why Other Options Are Wrong:
Because it is present only inside the nucleus: Protons are also in the nucleus and were still inferred earlier through other experiments, so this is not the main reason.
Because it is a fundamental particle: Electrons and protons are also fundamental in many senses; this does not explain the delay.
Because it does not move: Neutrons move and participate in nuclear reactions, so this statement is incorrect.
Because it is heavier than the proton: Mass alone does not prevent discovery; detection difficulty arose mainly from the lack of electric charge, not from mass.

Common Pitfalls:
Students often think the neutron was discovered late simply because it is located deep inside the nucleus, forgetting that protons are also nuclear particles. The key idea is that experimental detection depends strongly on charge. Neutral particles require indirect detection techniques through collisions or secondary effects. Remember that when comparing discovery histories, the ability of a particle to interact with detectors, especially via electromagnetic forces, is crucial.

Final Answer:
The discovery of the neutron was delayed mainly because it does not carry any electric charge, making it much harder to detect with early experimental methods.