Detailed Summary
The discovery of the electron is a critical milestone in the history of chemistry and physics that fundamentally altered the understanding of atomic structure. Before the realization that electrons existed, atoms were thought to be indivisible units, as proposed by early philosophers and later by John Dalton in 1808. Dalton's atomic theory laid the groundwork for later exploration but did not account for the new evidence of particle physics.
The journey towards the discovery of the electron began with experiments on electrical discharge in gases. Michael Faraday's work in the 1830s laid a foundation by demonstrating the particulate nature of electricity when it passed through electrolytic solutions. Later, experiments conducted in cathode ray tubes by Thomson in the late 1800s led to critical insights.
The most significant experiment was Thomson's cathode ray tube experiment, where he showed that cathode rays—streams of particles emitted from the negative electrode (cathode)—were composed of negatively charged particles, which he named electrons. His measurements established a charge-to-mass ratio for electrons, confirming their existence as fundamental components of atoms. Additionally, Millikan's oil drop experiment provided precise measurements of the charge on the electron, further validating the findings of that era.
This discovery not only revolutionized atomic theory by introducing the idea of subatomic particles (electrons, protons, and neutrons) but also paved the way for various atomic models, including those proposed by Thomson and Rutherford, which attempted to describe the structure and behavior of atoms.