J.J. Thompson and the First Subatomic Particle. The first discovery of a subatomic particle would come in 1897, when J.J. Thompson first discovered evidence for the existence of the electron. In the beginning of the nineteenth century, chemist John Dalton had, in the very first workable atomic theory, declared one of the fundamental principles of atoms – those tiny little particles that make up all matter in the universe – to be the fact that they were, by definition, indivisible. Before the end of that century, however, even before the entire scientific community had been convinced of the existence of these little things, the nature of atoms as the fundamental building blocks of matter was already being called into question. Atoms, it seemed, were made up of even smaller things.
Thompson’s Experiment
It was the British Physicist J.J. Thompson who is most often given credit for discovering the first subatomic particle – the electron. For the most part, this is true, but it should be known that the word itself had already been coined by Irish physicist George Johnstone Stoney (say his name out loud. It’s kind of fun) three years prior to Thompson’s discovery. Stoney had originally used the word in order to define a unit of negative electric charge.
Thompson’s monumental discovery of the actual particle which would be called the electron came in 1897 while he was experimenting with a cathode ray tube (an electronic device where a beam of particles are sent between a positive and a negative terminal within a vacuum tube, creating a peculiar light).
It was uncertain at the time exactly what sort of substance cathode rays may have consisted of, but Thompson’s experiments determined that it had a negative magnetic charge (he was able to bend the ray using a magnetic field and then measure the direction the ray bent so that he could determine both how much mass was involved and how it was charged). It became clear to Thompson that these rays were actually made up of tiny particles – particles which had a mass much smaller even than an atom (which could be determined by the amount of bending in a given magnetic field).
So for the first time, it had been determined that something smaller than an atom existed – in the form of tiny negatively charged particles, though it wasn’t immediately certain that these particles were actually part of the atom. They were at first seen to be a separate entity altogether.
Reaction to the Electron
Of course the scientific establishment at large wanted nothing to do with this discovery at first. They continued with their usual reluctance to accept anything that remotely differed from the scientific dogma of the day, holding fast to the simple, comfortable traditions of old, just as had their predecessors, whom they themselves so often derided for their archaic closed-mindedness.
Eventually, however, there was simply no other choice for most honest scientists but to accept the reality of electrons. One experiment after another was performed which proved conclusively the existence of these little things, though no one knew exactly what they looked like, or what their function was, or why they existed at all (many of the same questions we are still asking ourselves today).
Surely, J.J. Thompson himself didn’t know what he was getting into at the time – he certainly could never have realized the importance of his discovery. For electrons, it is now known, are fundamental aspects of the atomic structure. It is they who provide the necessary balance of charge in order to “neutralize” the atomic structure, and it is in them that all bonds form between atoms. In other words, without electrons, molecules would never form and atoms would stay separate. Complex matter, therefore, would never occur, and the universe would consist of nothing but a bunch of positively-charged nuclei, being pushed away from each other with all their like-charges.
Indeed, Thompson’s experiment was important, and kick-started an entire wave of discovery of sub-atomic particles, including the next step in understanding the atom – the discovery of the atomic nucleus.
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