Electrons were discovered by

Analyze the question: The question asks who discovered the electron, which is a history-of-physics question on atomic structure.

Explain the concept: Atomic structure was developed through several discoveries:

• Electron: discovered by J.J. Thomson in 1897 using cathode ray tube experiments. He showed that cathode rays were streams of negatively charged particles much lighter than atoms.
• Nucleus/proton: Ernest Rutherford (1911, gold foil experiment)
• Neutron: James Chadwick (1932)
• Laws of motion and gravity: Sir Isaac Newton

Step-by-step solution:

1. Option A, James Chadwick, discovered the neutron, not the electron.
2. Option B, J.J. Thomson, discovered the electron in 1897 through his cathode ray experiments. This fits.
3. Option C, Sir Isaac Newton, is known for the laws of motion, gravitation, and optics, and had no part in discovering the electron.
4. Option D, Charles Newton, is not associated with any such discovery.

Answer: The correct option is B. J.J. Thomson (the spelling in the question, "Thompson," is a common variant).

Exam tip: Remember the sequence with this pairing:

• Thomson → Electron (both have a "T" and "E" link: "Thomson's Electron")
• Chadwick → Neutron ("Chadwick Neutralizes")
• Rutherford → Nucleus ("Rutherford's Nucleus")

Questions on who discovered which particle appear often in JAMB, so keep this list handy.