A brief history of the electron concept

This article deals with the long theoretical and experimental way that has led to the modern concept of electron. In 1891 Johnston Stoney defined the electron as the elementary unit of the electrical charge. Around 1900 the first values of the charge and mass of the electron were deduced from experiment.The quasi immateriality of this particle pushed some physicists such Lodge to consider the electron as a moving tenseness of the ether. The heyday of the corpuscular electron took place in 1923 when a young American scientist Compton studied the collision between a photon and a free electron. This experiment was a brilliant proof of the light quanta theory of Einstein and it showed that photons and electrons behave as simple glass marbles. 3 years later Davisson and Germer showed clearly that electrons are diffracted by a crystal. This experiment was the first one to back up the fundamental concept proposed by the nascent quantum mechanics: the duality between wave and particle. (A.C.)