Electrons were discovered by

Analysis

The question asks for the scientist credited with the discovery of the electron, a fundamental subatomic particle.

Concept

In the history of atomic physics, several scientists contributed to our understanding of the atom. To identify the correct answer, we must look at the specific discovery associated with each scientist:

• John Dalton: Proposed the Atomic Theory, suggesting that atoms are indivisible spheres.
• James Chadwick: Discovered the neutron in 1932.
• J.J. Thomson: Conducted experiments with cathode ray tubes in 1897. He observed that cathode rays were composed of negatively charged particles, which he named "corpuscles" (later known as electrons).
• Niels Bohr: Proposed the Bohr model of the atom, which describes electrons orbiting the nucleus in specific energy levels (shells).

Solution

1. Evaluate Dalton: Dalton's model viewed the atom as a solid, indivisible sphere. He did not discover subatomic particles.
2. Evaluate Chadwick: Chadwick is famous for discovering the neutral particle in the nucleus, the neutron.
3. Evaluate Thomson: Through his cathode ray experiment, Thomson demonstrated that atoms contain smaller, negatively charged particles. This discovery fundamentally changed the view that the atom was indivisible.
4. Evaluate Bohr: Bohr built upon the work of others to explain the arrangement of electrons, but he did not discover the electron itself.

Based on historical scientific records, J.J. Thomson is the physicist who discovered the electron.

Conclusion

The correct option is C.

Exam Tip

To remember these easily for your JAMB exam, use this simple mnemonic:

• Proton = Rutherford (Gold foil experiment)
• Electron = Thomson (Cathode ray experiment)
• Neutron = Chadwick (Beryllium bombardment) Think: "PET-RC" (Proton-E, Thomson-Electron, Rutherford-Chadwick). Wait, actually, just remember "J.J. Thomson = Electrons" as a core fact, as it is a very common JAMB question!