Which scientist is credited with the discovery of the electron?

• A. Robert Millikan
• B. Niels Bohr
• C. Ernest Rutherford
• D. J.J. Thomson

Answer: (D)

Verified step by step guidance

1. Understand that this question is about the historical discovery of the electron, a fundamental particle in chemistry and physics.
2. Recall that the electron was discovered through experiments involving cathode rays, which are streams of electrons observed in vacuum tubes.
3. Identify the scientist who conducted these cathode ray tube experiments and concluded the existence of the electron as a particle smaller than an atom.
4. Recognize that J.J. Thomson is credited with this discovery in 1897, as he measured the charge-to-mass ratio of the electron.
5. Note that the other scientists listed contributed to different areas: Robert Millikan measured the electron's charge, Niels Bohr developed the atomic model, and Ernest Rutherford discovered the nucleus.