The Oddessey of the Atom: From Democritus to The Periodic Table. Part 1

veer vishal dubey
3 min readJul 30, 2021

Hello! Its been a while! Sorry for the inactivity, just had stuff going on , school, familty problems, so decided to take a break. However Im back! I plan to write a story every week and I thought it would be cool to introduce the story behind of how the atomic models came into existence and the physics behind it. What seems like a topic of chemistry was once a topic taken up by hardcore physicists. So lets talk about everything from Quantum Mechanics, the Photoelectric Effect and Wonderful Experiments and Observations to the Mordern Periodic Table. This series can have as many parts as I like, so I can bring you all the ideas!

The Early Days

The idea of atom was first disussed in detail by Democritus in Greece and Kashyapa in India. The central idea of the theroy they proposed was that there will be a limit which you cannot cross, when cutting matter in half and then in half again and so on. Like you cannot break a brick into two (you’re strong if you can do that) after you have broken it into crumbles, you can break the matter into two after that limit. The particle at the limit was called “atomio” by Democritus and “Parmanu” by Kashyapa.

Skip to the year 1808, when an English Chemistry teacher by the John Dalton proposed a new theory. It was basically a remastered theory of Democritus and he called the particle at the limit “atom”. He also proposed various theorems in his theory, which were later proven wrong. But little did he know, that a theory he developed for chemistry, would be an area of intesive physical research and also the origin of an entire new field of physics.

The Cathode Ray Experiment and the discorvery of Electrons

Skip for ward again by a hundered years or so. Maxwell had just published a new theory on electromagnetism. Scientists all over the world were trying to use it to explain many properties of matter. One such scientist was JJ Thomson. In 1898, Thomson was using a vaccum tube to hold a couple of carbon electrodes connected to a circuit and filling it with different gasses in hopes of finding a new element. He accidentally left a phosphorus sheet in the tube when changing the electrodes. Then as he fired up the circuit, he saw that the phosphorus screen lit up. According to Maxwell’s theory, the rays must have went from the Cathode to the Anode. He once again used different gasses and all of them showed the same result. This meant that there was a negatively charged particles that were travelling. He visualised these to be rays and named this stream of particles “Anode Rays” and the particle “electron”.

Discovery of the Proton

By modifiying the apparatus so that the screen was behind the anode, scientists were able to discover “Anode Rays” and the bundles of these rays were named “Protons”.

Discovery of the Nuetron

Neutrons were discovered in 1919 by James Chadwick. It is kind of hard to explain the experiment he used, because it uses teh principles of photoelectric effect, but he bombarded a thin sheet of Berillyum with α particles (alpha particles, which are Helium atoms without any electrons) and it produced a light. This was in accordence of photoelectric effect and hence an electrically neutral particle was discovered. This was named “Neutron”.

Alright this is it for now, next time up, we are going to discuss various models proposed!

--

--