Concept:The discovery of the electron is credited to J. J. Thomson.Explanation:In 1897, J. J. Thomson performed cathode ray tube experiments.He identified negatively charged particles and named them electrons.James Chadwick discovered the neutron.Ernest Rutherford discovered the nucleus and protons.Amedeo Avogadro is known for Avogadro’s law.Therefore, the correct scientist is J. J. Thomson.Answer:A. Joseph J. Thompson