Discovery of Electron

The electron was the first subatomic particle to be identified, by J. J. Thomson in 1897, through his experiments with a cathode-ray discharge tube — a sealed glass tube held at very low pressure with electrodes at either end. When a high potential difference was applied across the electrodes, a stream of rays travelled from the cathode (negative electrode) toward the anode (positive electrode); these came to be called cathode rays. Thomson showed that this stream consisted of very small, negatively charged particles, and — crucially — that these particles were present in every kind of atom he tested, regardless of what gas filled the tube or what material the electrodes were made from. He also found each of these particles to be roughly 1837 times lighter than a hydrogen atom. Because the same particle t …