Which subatomic particle was identified first in research using cathode ray tubes?

The identification of the electron as the first subatomic particle was a significant milestone in atomic theory. This discovery occurred through experiments conducted with cathode ray tubes in the late 19th century, particularly by J.J. Thomson in 1897. When an electric field was applied to the tube, the cathode rays—streams of particles—were deflected towards the positive plate, indicating that they were negatively charged. This led to the conclusion that these particles were much smaller than atoms and fundamentally different from the atoms themselves.

Thomson's work established the existence of electrons and provided insights into the atomic structure, leading to subsequent developments in the understanding of atomic theory. The other subatomic particles, such as protons and neutrons, were discovered later, with the proton identified in 1919 by Ernest Rutherford and the neutron in 1932 by James Chadwick. Quarks, which make up protons and neutrons, weren't theorized until the mid-20th century. Thus, the electron's identification through cathode rays laid the groundwork for modern atomic models.