Which British physicist discovered the electron in 1897?

J. J. Thomson discovered the electron in 1897 through experiments on cathode rays. His results showed that the rays consisted of tiny, negatively charged particles present in atoms.

At the Cavendish Laboratory in Cambridge, Thomson used improved vacuum tubes and tested whether cathode rays could be deflected by electric and magnetic fields. He compared their deflection and calculated a charge-to-mass ratio far greater than that of hydrogen ions, implying particles more than 1,000 times lighter than a hydrogen atom.

Thomson initially called the particles “corpuscles.” The word electron had already been proposed by Irish physicist George Johnstone Stoney in 1891, and later scientists adopted it. Thomson’s finding was revolutionary because atoms had commonly been treated as indivisible; it established the first identified subatomic particle.

The discovery is sometimes simplified as Thomson “finding” an electron in isolation. More precisely, he demonstrated the universal particle nature of cathode rays and measured their properties. In 1906 he received the Nobel Prize in Physics for his investigations of the conduction of electricity by gases.