Electron Discovered
J.J. Thomson discovered the electron, the first subatomic particle identified
April 30, 1897
Inside the Atom
In 1897, British physicist J.J. Thomson was experimenting with cathode ray tubes — glass tubes from which most air had been removed, with electrodes at each end. When a voltage was applied, a beam of particles traveled from one end to the other. Thomson showed through careful experiments using electric and magnetic fields that the particles in cathode rays were the same regardless of what metal the cathode was made from, or what gas remained in the tube. This meant the particles were a universal component of matter. He had discovered the electron — the first subatomic particle ever identified.
Measuring the Particle
Thomson measured the ratio of the electron's charge to its mass and found it was about 1,800 times lighter than the lightest atom, hydrogen. This was startling — if atoms contained something so much lighter than themselves, atoms were not the fundamental, indivisible units of matter that scientists had assumed since ancient Greece. Thomson proposed a "plum pudding" model of the atom: electrons embedded in a diffuse positive charge like raisins in a pudding. This model was later replaced by Rutherford's nuclear model, but Thomson's discovery that atoms had internal parts was the crucial first step.
The Particle That Runs Technology
The electron is the particle responsible for electricity, chemical bonding, light emission, and magnetism. Every electrical current is electrons in motion. Every chemical reaction involves the rearrangement of electron bonds. Every computer chip manipulates electrons. Thomson won the Nobel Prize in Physics in 1906 for his discovery. Decades later, his son George Thomson won a Nobel Prize for showing that the electron behaves as a wave — father and son each earning a Nobel for revealing a different face of the same particle. The electron is the foundation of the modern technological world.