Neutron were discovered by

Analysis

The question asks for the scientist credited with the discovery of the neutron, a subatomic particle found in the nucleus of an atom.

Concept Explanation

To answer this, we look at the history of atomic structure:

• J.J. Thomson: Discovered the electron in 1897 using cathode ray tubes.
• James Chadwick: In 1932, he performed an experiment bombarding beryllium atoms with alpha particles. He observed that a neutral radiation was emitted, which he identified as the neutron.
• Michael Faraday: Known for his work on electromagnetism and electrochemistry, not subatomic particle discovery.
• John Dalton: Proposed the atomic theory in the early 19th century, stating that atoms were indivisible spheres; he did not discover subatomic particles.

Step-by-Step Solution

1. Evaluate the options: We eliminate Dalton (atomic theory) and Faraday (electromagnetism).
2. Compare Thomson and Chadwick: Thomson is famous for the "Plum Pudding" model and the electron. Chadwick is specifically famous for proving the existence of the neutron, which had been theorized but remained elusive because it carries no electrical charge.
3. Conclusion: James Chadwick’s experimental evidence in 1932 is the universally accepted scientific discovery of the neutron.

Exam Tip

A simple mnemonic to remember these discoveries:

• Proton = Rutherford
• Electron = Thomson (Think: "T" for Thomson, "E" for Electron)
• Neutron = Chadwick (Think: "NC" for Neutron Chadwick)